This must have been a concession to existing Web pages, because it was added to HTML 4.0 and deprecated at the same time. You shouldn't be underlining things in the first place. I haven't looked these up yet, but i have a feel for the sort of thing that W3C looks down upon. Use comments correctly. And then some.
Incorrect usage can result in blank pages on some browsers.
Correct usage can result in parts of comments being displayed on other browsers. If your Navigator is 2.2 or earlier, or your Internet Explorer is 3.0 or earlier, please upgrade. It's one thing to try to accommodate various browsers, but i suspect that most HTML authors are fed up with other people's bugs. Look at some well-commented SGML code, and suddenly the syntax seems appropriate. The Unofficial WebTechs Validator FAQ .