"" or not ""
 

I've noticed some use " " in their html and some don't. For example...

<table width=100 cellspacing=0 cellpadding=3>
<!-----other code-----!>
</table>

I use " " wherever I specify something, I always assumed that was "correct". Am I wrong?

I think HTML 4.01 requires quotes on attribute values. I'm not sure.

Quotes are preferable, though. In XHTML, they are required.

Proper HTML requires the use of double quote marks around the value of all parameters. Defective browser implementations have allowed sloppy HTML to get away without the double quotes but any good validator like HTML Tidy will point out any such code as incorrect.