When upgrading from 1.7.3 to 2.5.0, the Control Panel may appear "broken" after the upgrade. See the image to the right.
This issue is caused by changes to the Administrative template.
How to Fix
The fix is to clear your browser's cache.
- Mozilla / Firefox / Safari: hold Shift while clicking Reload, or press either Ctrl-F5 or Ctrl-R (Command-R on a Macintosh); Konqueror: click Reload or press F5; Opera: clear the cache in Tools → Preferences; Internet Explorer: hold Ctrl while clicking Refresh, or press Ctrl-F5.