UML has a jungle of Diagrams.Profile Diagrams, Class Diagrams, Package Diagrams...However, (IMH-and-not-too-experienced-O) I quite see that doing each and every diagram is  overkill.Therefore, which UML Diagrams are more suitable in a web context, more expecificly a blog (we want to build it from scratchs).I understand that just because I used UML Diagrams does not imply that our code would be great and brilliant... but, it certainly would be better than just unplanified code...
Truly useful UML diagrams
web development;design;uml
As a general guideline:One deployment diagram for an overview of the architecture (good for any system)One use case diagram for an overview of what users will do with the system (dito)One class diagram for the data modelActivity diagrams for the flow of individual use cases if they are complexPerhaps a state machine diagram if you have a create/review/publish workflow for blog entriesSome diagram types (e.g. timing diagram) have rather specialized uses, others tend towards a level of detail where actual code does a better job (e.g. sequence diagrams), and others yet seem to be intended for gigantic projects but have questionable utility even there (package diagrams? Any IDE can show you your packages).