Basic HTML Question - Please help clarify

Attributes - MUST they be withing quotation marks?

[martinibuster]

Thanks,
Just trying to clarify this with someone else.

[Knowles]

I think to validate they have to be, as long as its HTML and not XHTML I think you can get away with not doing it. I would say its best to go ahead and do it.

[marek]

In HTML the attrubute values need not be quoted, provided they do not contain whitespaces. In XHTML all attrubute values have to be quoted. It's a good idea to quote all attribute values even in HTML because of forward compatibility.

[g1smd]

In HTML 4.01, when using 0 to 9 and A to Z only, they don't have to be quoted, but W3C recommends that they all are.

In XHTML they must be always quoted.

In any HTML version, if the string includes any other characters than 0 to 9 and A to Z, it must also be quoted e.g. color="#FF00FF"

If there is any white space in the attribute it must be quoted.

[martinibuster]

Good answers, thanks.

Although there's probably no way to say so definitively, I think that it may not be too unreasonable to think having no-quote attribues may contribute to a spider incorrectly understanding what's on the page.

Or am I being paranoid?