Resizer

Resizer is a bookmarklet that resizes the size of the screen for responsive design testing.

resizer An Useful Bookmarklet For Responsive Design Tests Resizer

It’s very easy to use and features standard screen sizes like 320×480 (mobile), 460×640 (small tablet), tabled (768×1024), and others.

Resizer is also available as a Chrome plugin and is without a doubt the bookmarklet if you’re designing responsive pages.