Is there a manual or the like that I have missed which documents this command, \installpagebreakhandler, and others such as \useURL and \setupinteraction? (I am interested in the latter, because inserting a blue, underlined URL for email in my output has curiously enough turned by footnote numbers blue.)
no, these commands are not in a manual, but one can find them in the source code; the \install.. ones are real low level; the \definepagebreak[whatever][yes] one is public.
Regarding the rest (some hints to play with): \useURL [context] [http://www.pragma-ade.com] \goto{Pragma ADE}[URL(context)] \setupinteraction [state=start, color=black, style={\tf\underbars}] \setupunderbar[alternative=c, rulecolor=blue] % underdots Footnote numbers are interaction links, too. I don't know how to handle them different. But you can switch off footnote interaction somehow AFAIK. Grüßlis vom Hraban! -- http://www.fiee.net/texnique/