Is Align Attribute Valid for P Element in XHTML or not?

It seems that in even years the align attribute is allowed and then in odd
years it's not.

I am trying to use XHTML because I want to use MathML, and getting the
DOCTYPE declaration and the 'html' element written properly is like trying
to pull hen's teeth. Indeed I am copying the DOCTYPE and html and mathml
elements into a page which does not render, but it renders on the page from
which I copied the source! How does that (not) work?

"Beauregard T. Shagnasty" <a.nony.mous (AT) example (DOT) invalid> wrote in alt.html:

SMH wrote:

It seems that in even years the align attribute is allowed and then in
odd years it's not.

Depends on whether or not you are Strict or Transitional.

p class="pcenter">This would be centered.</p

.pcenter { text-align: center; }

So with strict, no, right?
With transitional, it's wink-wink, right?

I suppose as strict as XHTML is---with all the required closing tags for
all elements----then "deprecated" for an attribute or element really means
"absolutely verboten."

I am trying to use XHTML because I want to use MathML, and getting the
DOCTYPE declaration and the 'html' element written properly is like
trying to pull hen's teeth. Indeed I am copying the DOCTYPE and html
and mathml elements into a page which does not render, but it renders
on the page from which I copied the source! How does that (not)
work?

Are you using a proper mathml doctype?

http://www.w3.org/QA/2002/04/valid-dtd-list.html

!DOCTYPE math SYSTEM
"http://www.w3.org/Math/DTD/mathml1/mathml.dtd"

..for example

I think this would be so IF I was only using MathML in the document.

However, I am mixing (X)HTML and MathML together, and these mixed
declarations are possible.

The W3 Validation service is not being helpful.