Various programming languages use different ways of commenting, so just be careful what language you're in.
Java (and JavaScript follows the same method, which is why you've seen it in scripts) and C++:
Code:
// Only this line is a comment
/*
Whatever's between the two is a comment
*/
HTML:
Code:
<!-- This is a comment -->
CSS:
Code:
/* This is a comment */
VBScript
:
Code:
' This is a comment
ColdFusion:
Code:
<!--- This is a comment --->
Perl:
Code:
# This is a comment
C:
Code:
// This is a comment
... and the list goes on.
-Shane