Script Summary: Splits browser window into two iframes displayed next to each other
This script displays the current page in a split screen view, using two iframes placed side-by-side.
It is useful for browsing source code files, when it's often convenient to be able to look at two parts of the code that are related, but are many lines away -- like, a function definition and the place where the function is called.
Usage: Go to the "User Script Commands" menu and select "Split screen view".
A screenshot of the script in action, displaying a source code file on GitHub: