in fig1 a conventional web - based cobrowsing system is shown . a cobrowse server 4 acts as a web proxy running in between an origin web server 5 and all the participants 3 in the same cobrowsing session . for instance , the cobrowse server 4 first fetches a page content from the origin web server 5 and for example injects a piece of javascript code into the page for enabling a cobrowsing service before forwarding the modified webpage to all participants 3 . further the cobrowser server 4 coordinates data traffic via the document object model 11 and for exchanging events 10 between the participants 3 . to initiate a conventional cobrowsing session a session creator 2 , being a participant of the created cobrowsing session initiates such a session and interacts with the cobrowse server 4 for providing the created cobrowsing session to the other participants 3 . fig2 shows a system according to a first embodiment of the present invention . in fig2 an architecture of a privacy preserving cobrowsing service according to an embodiment of the invention is shown . in contrast to the system of fig1 the origin web server 5 is directly connected ( reference sign 20 ) to the session creator 2 . the session creator 2 is connected ( reference signs 10 and 11 ) via the document object model interface respectively for event coordination and via the cobrowse server 4 with the other participants 3 . in general the origin web server 5 may be a standard web server delivering a web application . for instance the origin web server 5 may be a content provider or an insurance company delivering services to their customers via the internet . the origin web server 5 may be independent of the cobrowse server 4 . to enable a privacy preserving cobrowsing service the origin web server 5 may put an indication , like a “ cobrowse ” button into provided webpages , so that the privacy preserving cobrowsing service can be triggered when a session creator 2 clicks the “ cobrowse ” button for initiating such a service . further , the origin web server 5 may provide cobrowsing support scripts implementing one or more parts of the cobrowsing functionality to preserve privacy . the session creator 2 may in particular be a browser client rendering a web page provided by the origin web server 5 . the session creator 2 may operated by a user creating a cobrowsing session . furthermore the session creator 2 may provide or execute scripts which may be provided by the origin web server 5 implementing parts of the cobrowse functionality to preserve privacy . these scripts may contain a proxy delivering requested webpages and other data from the origin web server 5 to the cobrowse server 4 , so that the other participants 3 in the same cobrowsing session can join the session . these scripts can mask private data , so that the session creator 2 does not send out the private data to the cobrowse server 4 and the other participants 3 . further different private policies may be applied by the script ( s ) or a session creator 2 may decide what data should be transferred via the cobrowse server 4 to the other participants 3 . events related to private data in an application are not sent to the cobrowse server 4 and the other participants . such events may for example be an entry of a new bank account number or the like . the cobrowse server 4 provides the functionality to collaboratively browse for example a webpage provided by the session creator 2 . the cobrowse server 4 in particular is operable to forward a masked webpage from the session creator 2 to the other participants 3 , act as a proxy for the other participants 3 to fetch the content of for example embedded static objects in the cobrowsed webpage from the session creator 2 on requests and synchronize events occurring on the masked and shared page with other participants 3 , so that users in the same cobrowsing session can still share their interactions , for example mouse moves , scrolls , clicks or the like . the participants 3 participate in the cobrowsing session , for example via their browser clients . they can see only a version of a webpage comprising no private data , because the private data has been already masked by the session creator 2 . therefore the first user / the session creator 2 have full control of the private data . this is ensured by making all communication first go through for example a browser of the session creator 2 . the cobrowse server 4 is no longer in between the original web server 5 and the participants 3 compared with conventional systems . the cobrowse server 4 is only between the session creator 2 and the other participants 3 whereas the session creator 2 has direct connections with the origin web server 5 . further private data can be masked by the session creator 2 , so that other participants 3 can still cobrowse together but without disclosing private data . even further cobrowsing is enabled for both http - based non - secure web services and https - based secure web services , because the cobrowse server 4 is only between the session creator 2 and the participants 3 and not compared with conventional systems in between the origin web server 5 and the session creator 2 . therefore there is no need to break https connections in between them . fig3 shows a part of a method and a system according to a second embodiment of the present invention . in fig3 a basic work flow of a privacy preserving cobrowsing service is shown . in fig3 a system according to fig2 is shown in more detail . the origin web server 5 comprises a rule specificator for specifying private data . further a cobrowse button is embedded into data responses , for example webpages . the cobrowse button may be provided in form of javascript code files given by the cobrowsing service provider to provide functionalities of privacy preserving cobrowsing service and could be reviewed by others to check whether they are doing what they are supported to do for the purpose of accountability . in fig3 two javascript code files to enable privacy preserving cobrowsing , controller . js and participants . js are used . the javascript code files are used by the session creator 2 by executing them . the cobrowse server 4 comprises an event coordinator for event synchronization between the session creator 2 and the other participants 3 . the participants 3 execute the javascript code file participant . js . the javascript code file participant . js is used by all users , i . e . the participants and the session creator , in the same cobrowsing session for synchronizing user interactions on the shared webpages . in a first step s 1 the first user respectively the session creator 2 fetches a cobrowsed webpage comprising a cobrowse button and the javascript codes participant . js and controller . js will be triggered to start privacy preserving cobrowsing service when the session creator 2 clicks on the cobrowse button . preferably the javascript code file controller . js will fetch in a second step s 2 the rules / specification defined by the provider from the origin web server 5 and apply them into the current requested webpage , so that the first user can visually see which part of elements in the current webpage are initially masked as private by the web service provider of the origin web server 5 . in a third step s 3 the first user respectively the session creator 2 can mask further elements which might contain some private data from his prospective or might remove predefined masked elements . in a fourth step s 4 via a first channel c 1 after the first user respectively the session creator 2 finishes masking private elements on the current web page and confirms to start a cobrowsing session with the other participants 3 , the session creator 2 will contact the cobrowse server 4 and get for example a unique session id for the current web page in return . contacting the cobrowse server 4 by the session creator 2 via the first channel c 1 requires cross - origin communication supported in particular by most standard browsers . in a fifth step s 5 the session creator 2 generates a key for data exchanging among all participants 3 in the current cobrowsing session , uses the session id and the generated key to construct a session url and then spreads the generated session url to other participants 3 through a second communication channel c 2 . the second communication channel c 2 may be for example provided by a social network , a mail service or some service provided by the origin web server 5 and different from the first communication channel c 1 . in a sixth step s 6 the other participants 3 get the session url and start to join the masked cobrowse webpage through the cobrowse server 4 after clicking the session url . in a seventh step s 7 the cobrowse server 4 asks for the masked webpage from the session creator 2 and transmits the masked webpage to the other participants 3 upon receiving the joining request from the other participants 3 . the javascript module participant . js is injected into the masked webpage for event synchronization between the first user respectively the session creator 2 and the other participants 3 . additionally to prevent the cobrowse server 4 or any intermediate attackers from seeing the masked webpage , the session creator 2 can encrypt the masked webpage with the generated key before sending the masked webpage out . therefore only participants 3 who have the generated key can see the masked webpage . in an eighth step s 8 the other participants 3 receive the masked webpage and may also request the external objects embedded in the received webpage from the cobrowse server 4 like static images , css files or the like . these external objects may be forwarded by the cobrowse server 4 from the session creator 2 to the other participants 3 . if the session creator 2 cannot fetch these requested external objects from its local cache the session creator 2 will refetch them from the origin web server 5 and transmit them to the cobrowse server 4 for forwarding them to the participants 3 . in a ninth step s 9 the first user respectively the session creator 2 and the other participants 3 now start to interact with the current web page for experience sharing or collaboration . the interactions will be synchronized by the injected javascript module participant . js and coordinated by the event coordinator in the cobrowse server 4 under consideration of their slightly different webpages . in other words the first user respectively the session creator 2 is used as a proxy to control which part of a requested page or application to share with others in the same cobrowsing session . the first user first fetches the content and has full control of which part of content to show to the other participants 3 in the cobrowsing session . the first user keeps a full control of his / her private data within the cobrowsed webpage and the session creator acts as a special type of proxy for all the other participants 3 . all requests issued by the other participants 3 will go through the session creator 2 and via the cobrowse server 4 . marking private elements can be performed by the first user 2 who creates the co - browsing session . for example the first user may specify private data on its browser by choosing which part of content to hide before the other participants join the cobrowsing session . the second option is to mark data as private elements by the origin web server 5 . for example the owner of the origin web server 5 can use an external file associated with the cobrowsed page to specify which elements in the page are private or which additional property elements must have to be marked as private elements in the page . before the first user fetches the webpage for starting a cobrowsing session the origin web service provider can mark the webpage to specify which part of the page is supposed to be sensitive for their customers . this part of content can be automatically regarded as private element when some users establish a cobrowsing session for that page . an external file associated with the page can be created by a web service provider to define the private elements in the page for example through a declarative script language which can be interpreted by the session creator 2 . further , the first user may mark private data before the webpage is transmitted to other participants 3 . the first user may visually see which parts of elements are already marked and can also continue to mark some other elements in a visualized way . to improve user experience global policies as part of a requested document , for example a html - document may be defined , so that for example they do not propagate form data or do not show text in tables or using a html query language for defining what should be replaced , for example webquery . using such a language enables more flexibility . to check the masked private data a test mode for the first user respectively the session creator 2 can be provided . the first user can then see what information the other participants 3 can actually see to make sure that the private data have been correctly masked . for example this can be provided that upon a click on a bottom or a special key on a keyboard or any other input the user can switch between a masked and a non - masked version of the requested webpage . a template can be provided to the users to reuse some pre - defined masking rules , i . e . the rules / specifications which elements are considered as private data and will be masked . also different parts , for example of a html - document , can be marked as private for different participants , so that each participant can see his / her individual view on private data allowing an individualization for each participant corresponding to an assigned “ security level ” for each participant . to execute hiding the private data associated with the masked private elements is modified and for example replaced with some non - sense data according to the type of the private elements . in the table below examples for rules for this masking are shown . these rules ensure that private data is masked but still allow synchronization of a multiuser web session : of course further rules can be added masking data or attributes of other tags , preferably similar as described in the table above . to avoid that other parties cannot see — additionally to the masked private data — other web application data , https - based connections between all communicating entities or components may be used . https - based connections can easily be implemented since for example — in all modern browsers https is supported . another option is to use an asymmetric cryptographic method , for example public key / private key encryption together with an external party acting as a certification authority . this makes sure that each participant in the multiuser web session is the one he / she pretends to be and that only these participants can en -/ decrypt exchanged data . this allows for example that the cobrowse server 4 cannot see any web application data exchange between the participants 3 of the multiuser web session . the cobrowse server 4 comprises also — as mentioned above — an event coordinator operable to synchronize user interactions over the shared webpage with masked private data , so that the first user / session creator 2 and the other participants 3 are able to share their activities on the browsed webpage for example without disclosing the masked private data to the other participants 3 . the event coordinator is in particular operable to coordinate the needs of the participants 3 to work on slightly different webpages : for example the event coordinator in the cobrowse server 4 avoids the propagation of the update events associated with the private data of those marked private elements . in summary the present invention enables the first user / session creator 2 to keep control which part of content of a page in a multiuser web session to share with other participants in the same session . the present invention further enables the web server 5 as well as the first user / session creator 2 to be able to mark private elements within a cobrowsed webpage . even further the present invention enables an element - adaptive obfuscating method to hide private data associated with each private element before for example a cobrowsed page being sent out from the first user / session creator 2 to the other participants 3 . the first user therefore prevents both the cobrowse server 4 and the other participants 3 from seeing her / his private data . the present invention has inter alia the following advantages : private data is hidden from third parties in a multiuser web session . both normal pages like webpages and secure pages are supported architecturally for browsing in a multiuser web session . further cobrowsing for https - based web services is also supported . many modifications and other embodiments of the invention set forth herein will come to mind the one skilled in the art to which the invention pertains having the benefit of the teachings presented in the foregoing description and the associated drawings . therefore , it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims . although specific terms are employed herein , they are used in a generic and descriptive sense only and not for purposes of limitation .