Dear Lars, A propos of your message to categories, I really cannot understand why anyone would want to use any (existing) language other than LaTeX for writing mathematics. HTML and its developments seem to me to be much less expressive and much more bureaucratic, especially for writing (ordinary) mathematics. That readers using the web have inferior browsers is, to me, an argument for developing and promoting better browsers, not for forcing mathematical authors to use worse mark-up languages. With existing web technology, there are ways of putting LaTeX formulae, diagrams, etc on web pages by translating them into PostScript and then GIF files (LaTeX2HTML does this). For simple mathematical formulae, TTH makes full use of the (limited) features of HTML, without using GIFs, and is what I used to translate my book into HTML (though I had to write a substantial program to simplify by LaTeX before TTH could cope with it). Regarding diagrams, my view is that there is no "generic" diagram problem - particular kinds of diagram are for me two-dimensional variations on particular kinds of formal languages. My own TeX package does a good job of commutative diagrams for certain (but not all) parts of category theory. It is conceived as a way in which to write two-dimensional formulae, not as a way of "drawing". Paul http://www.dcs.qmw.ac.uk/~pt/diagrams http://www.dcs.qmw.ac.uk/~pt/book ("Practical Foundations of Maths")