Can't make transparency work with white

Thanks for the .png suggestion - solves the problem, plus I can go back to using \color{white} instead of \fg_f2ffff. I didn't know that .png had this alpha channel advantage over .gif.

About my [latex] code implementation, yes I use CodeCogs. I can't say I did a thorough search, I only poked around the Internet for an hour or so, but amongst what I found you had the most complete solution.

In my [latex] code implementation, message previews replace the [latex] code with an HTML img tag which uses the CodeCogs Latex URL. When a message is finally posted then I actually store the returned image as a permanent image file so that your engine doesn't receive a request every time the message is viewed, and the HTML img tag is changed to reference that image. Saving a copy of the image file also guarantees that if your server is down or if you discontinue the service that existing messages with Latex expressions will still display properly.

--Percy