My page validates XHTML 1.0 Strict.
But when i check using the HTML Tidy extension in Firefox.

It does not allow <p></p> empty tags

I'm using it for vertical spacing.

what is an alternative to it?

<div style="padding:10px"></div>

That's just so dumb to me, even though it's semantically correct. Compare that length to <p></p>

Should i ignore html tidy?

If you write good (x)html from the start you wont need a program to tidy up for you ;)

An empty paragraph doesn't make sense. You shouldn't be using it for "veritcal spacing" as the spacing of paragraphs will vary from UA to UA.

Instead, use a div, or a <br /> tag.

Just because something validates, doesn't mean its semantically correct, and using <p></p> for vertical spacing is definately not semantically correct.

Yeah. i've changed to div and html tidy is happy now

YES! FINALLY! now ALL my pages are XHTML 1.0 Strict COmpliant. Whew!