This is a fun little bookmarklet I made while exploring different ways to generate website layouts at Designly. It simply turns each div into a colored block, getting slightly darker when they start to overlay each other. Here's a few examples:
Pinterest
Hacker News
Google
To try it, simply click the following link and to install it drag the link to your bookmarks and it will be available on every webpage: X-Ray
The source code is available on Github.