This is simple extension that inserts custom JavaScript and CSS code into each web page, allowing you to modify the way it behaves and looks.
You can download and install directly from the Google Chrome webstore.
The default installation does nothing. You'll have to provide the script and stylesheet yourself.
To edit the script and stylesheet, go to chrome://extensions and click Options under Custom Stylesheet & Script.
The text areas in the Options tab will automatically save as you edit. Existing pages are not affected until refreshed.
Note: jQuery is no longer included and cannot be used in the custom script anymore.