Vertical Rhythm is the spacing and arrangement between words as a user reads down the page. On the web, this is a difficult thing to get right, even with tools like Compass assisting. The problem really comes in when you have multiple columns of text. If you want text lines to consistently land in the same places, you really need a visual aid that you can quickly drop in at any point as a reference.
This is where the Gridwax bookmarklet comes in; Once you’ve got it secured on your bookmark bar, you can drop the overlay on your site, and use hotkeys to quickly adjust it to match your baseline.
Where to get it: gridwax.gs
shift+up
shift+down
shift+left
shift+right