Q:

Signing into Google account refreshes already open webpage

I have noticed that signing into my Gmail account, automatically causes some webpage to refresh. For example, signing into Gmail while keeping http://poetsandquants.com/2014/01/10/the-spaceship-enterprise-comes-to-yale/ open in another tab causes the page to refresh once signin/out is done.  

How is this done?  
I am guessing this is some sort of tracking mechanism. Is this a known "feature" and legal?

How can I implement this for my own website?

A:

Once you sign in with your browser to your google account, all the open webpages with a Google +1 button automatically refreshes(same case here for the link you provided). This is not implemented by the website perse. Rather, this is a property of the Google +1 button. The Google +1 button is inserted as an iFrame in the page, with a javascript code that somehow initiates a refresh of the iFrame and/or the original page. Details, somebody with js knowledge can firebug an example page and tell you. This is done so as to prevent users from +1ing a post two times. The default colour of the +1 button will be white/transparent and once you +1 it, it turns red preventing further +1ings. Refreshing the page upon login prevents this from happening. 
This is known feature and because it is done by mighty Mr.G, we will have to think that this is legal. 
In order to implement this on your website, you will have to add a Google +1 button to your site.  

