Update:Check out the new BETTER java version!!!
In browser close-up font comparer.
Enter a few letters or a word, and submit to see the letters in two fonts overlayed and close up to show differences.
Currently only compares Helvetica and Arial. Using the default serif font as back up (to make it obvious that the browser does not support either Arial or Helvetica).
Tested for Safari 3 and Firefox 3
Here's the css that I'm using to overlay the two fonts: overlap.css
Please Contact me if you have any ideas to make this better. I especially am looking for a way to overlay text with html with out using "position: absolute"