Most likely there will be a center page for each of the main pages of the site.
This will look fairly bare and simply make calls to other jsp and java files which create their certain sections of the page.
Therefore you can see it as follows:
mainpage.jsp makes calls to :
titlejsp ->creates title
navigationjsp -> creates menus
maincontentjsp -> creates main content of page
footerjsp -> creates footer
miscutilsjsp -> probably can ignore *for background work*
This is simply an example and without the project's code I cannot advise you any further, but its bound to be similar!
Your use of java struts implies you are using the MVC approach - Model, View , Controller.
As the UI guy you are probably handling View and Controller of the model.
Therefore you will want to get an understanding in your project of what pieces supply the data *these consist of the model* and how those are to be viewed.
The Model holds the data
The View is the view onto the data
The Controller handles modification of the model
Hope this helps!