The prohibition of certain tags here has been on-going for a while and has been a gradual process. Some, like the script tag which went in my Joe Clone days, I can see as posing risks to a site, some like the img one I guess can slow loading down and some I suppose as Jeri indicated can be annoying although I do think table can be useful...Whatever, the powers that be have to set their own levels here and I would imagine they do wish to allow enough to help in communication, e.g. bold, italics, blockquote, etc. (although many people communicate effectivelly in pure text-only formats...) I also appreciate that mistakes in HTML involve someone else tidying up may be a factor.
Overall, I can't help feeling if Mudcat is only allowing a subset of HTML, that should be documented in the FAQ.
Jon