404 - File or directory not found. The resource you are looking for might have been removed, had its

Only one of my bookmark tabs is causing this to happen. Everytime I click on it, and even if I go to the original website and click the area I want, I still get this message"

404 - File or directory not found. The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable." 

All other tabs and bookmarks work fine so how do I reinstate the tab/browser page that I'm having trouble with? I'm using an imac running osx 10.7.5