That's the code I wrote for a bookmarklet that I call 'Frameit'. You can copy the above code to a bookmark in Firefox, (get rid of the newlines of course). Clicking on it encapsulates the current page in a frame surrounded to the left and right by black frames. The frames are resizable. For a lot of pages, this improves the readability as the number of words per line is reduced and the background is black and uncluttered. It's great for reading books and documentation in kiosk (F11) mode.
- Does not work with Internet Explorer (and I would really want it to because you cannot view HTML Help files in Firefox.) Updated code to make it work on Internet Explorer and Firefox.
- Does not work on certain sites like Wikipedia, which seem to explicitly disallow framing.