comment

COMMENT Element | comment Object (http://msdn.microsoft.com/workshop/author/dhtml/reference/objects/comment.asp): huh, they don't actually show the syntax; so what is it... "<COMMENT></COMMENT>"?

Alright, I think this pretty much confirms it: ;)
Code within the SCRIPT block that is not contained within a function is executed immediately as the page is loaded. To keep scripts from being displayed on down-level browsers, nest the SCRIPT block within a COMMENT block.