Andy, > Straight from the source: > > "In CSS2, identifiers (including element names, classes, and IDs in > selectors) can contain only the characters [A-Za-z0-9] and ISO 10646 > characters 161 and higher, plus the hyphen (-); they cannot start with a > hyphen or a digit." > > http://www.w3.org/TR/REC-CSS2/syndata.html#q4 True, except that this was amended in the CSS 2 errata document last year to include underscores [1]. The problem is that a number of legacy browsers do not handle underscores because they were for quite some time considered illegal (however IE/Win32 has always allowed them, I believe). So, the bottom line: underscores _are_ legal in id and class names, but their use is ill-advised unless the developer knows that they are actually supported in targeted browsers (such as on an Intranet). Eric Meyer has written a pretty good article on using the underscore in class and id names on Netscape's DevEdge site [2]. James Aylard 1. http://www.w3.org/Style/css2-updates/REC-CSS2-19980512-errata.html#x3 2. http://developer.netscape.com/evangelism/docs/technotes/css-underscores/