no change in template in browser

I’ve changed some tekst in a template, but i cant see the changes in my site when i view it in my browser (IE7). Like categories -> categorieen. The php files are changed, but the site still shows the old text instead of new text. When i aplly the changes on the default template of wp, it is processed, but when i try to do the same on 3rd party themes, no change is processed.