This macro is just a reformatted version of mfranken's
HTMLMacro. Ok, so, why did I go through the trouble of reformatting existing code? Well, because I found mfranken's version only after having written my own little clumsy buggy version, so I just changed the couple of lines I needed to fix in my copy and kept that version as it is part of our integrated packaged (I hate nothing more than a distribution composed by mix of disparate sources). Oh, I was too lazy to export the description to the external messages file (it makes our copy less portable, but also less coupled with the SnipSnap source code).
So..... just look at mfranken's original post for any detail. Hopefully this snip will only attract your attention to the existence of that simple yet sooooooo useful macro.