Sometimes, espeially while you work on your theme, you have to clear smarty cache to see changes that you applied to theme files. It's necessary because smarty cache "remember" old template files. To "refresh" smarty memory you have to clear smarty cache. After that - all informations stored in cache will be "recompiled" with new template files. You will see all changes that you made then.
Clearing smarty cache
Whole process is very easy. Just log in to back office, then go to adv. parameters > performance menu item. You will see there form to manage performance option. There is (presta 1.6: in the top right hand side, presta 1.5: below the cache input field in form) a button to clear it (smarty). Just press it, after a while your smarty will be cleaned up. Then just refresh your front office.