May use in HTML doc(DTD), XHTML(DTD) tags ?

[leonidassavvides]

May use in HTML doc(DTD), XHTML(DTD) tags ? When this page rendered (HTML) in a newest browser the xhtml will appear [or i must have XHTML(DTD) doc) ? In an old browser they just ignored ?
eg.
<input type="button".... />
<br />

[Medyman]

Hmm...your English isn't clear but I think I understand.

There is nothing stopping you from using XHTML syntax with an HTML doctype. The page, in terms of content will be rendered identical.

The problem you'll have is that the HTML won't validate -- thereby perhaps putting browsers in quirks mode and throwing off any CSS styling.

[djr33]

Medyman is correct. But I don't understand why you want to. If you do that, you will have invalid code. It won't help.