404 on pages

Hello,

I seem to get alot of 404 errors when navigating back, for example

this page

http://somervillecover.com/index.php/community/categories/19-stores-shops-and-boutiques-2/latest

if I were to navigate to http://somervillecover.com/index.php/community

then select in categories "stores, shops, and boutiques"

all is good but if i were to select a page for example "shades" and then hit the back button i get :

404 Sorry, the page that you are looking for is not found.

with the address of http://somervillecover.com/index.php/community/categories/19-stores-shops-and-boutiques-2/latest