From Danny Goodman's Dynamic HTML: The Definitive Reference (2nd Ed, p253):
Support indicated here for Netscape 6 is based on the browser's DOM implementation. The DOM reports to scripts that the colgroup element and its attributes exist (reflected as properties). But as of Netscape 7, the element does not perform its intended tasks. A later version will likely connect the element's internal wiring.
And colgroup's attributes support is as...
align: NN n/a IE 3 HTML 4
char: NN 6 IE n/a HTML 4
charoff: NN6 IE n/a HTML 4
span: NN n/a IE 3 HTML 4
valign: NN 6 IE 3 HTML 4
width: NN 6 IE 3 HTML 4
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0 (CK-SillyDog)