Resize your browser to various standard resolution sizes.

The Browser Window Resizer is is an addition to the right-click menu for Firefox useful for testing different screen sizes. It accurately resizes your browser so you can test to see what a web page looks like in all of the standard resolution sizes.Supports the 640x480, 800x600, 1024x768, 1280x1024, 1600x1200 resolutions.

Resize the current page via the Context menu (Right-Click), Tool menu or Toolbar button.

Ссылка: http://releases..b/mozilla.org/extensions/window_resizer/window_resizer-0.5.1-fx.xpi