Forums / Cotonti / Skins / XTHML Validation

I am making a new skin and I am trying to validate it.
It passed the CSS 2.1 validation test. However, it seems I cannot get the XHTML validation - either strict or transitional or even frameset.

Some errors are my fault - like to omit the alt attribute for images. There are some others I am puzzled by. For instance:

 Line 67, Column 50: reference to entity "a" for which no system identifier could be generated 
<p><form id="search" action="/plug.php?e=search&a=search" method="post">✉ 
This is usually a cascading error caused by a an undefined entity reference or use of an unencoded ampersand (&) in an URL or body text. See the previous message for further details. 
 Line 67, Column 47: entity was defined here 
<p><form id="search" action="/plug.php?e=search&a=search" method="post"> Line 67, Column 72: document type does not allow element "form" here; missing one of "object", "applet", "map", "iframe", "ins", "del" start-tag 
…="/plug.php?e=search&a=search" method="post">✉ 
The mentioned element is not allowed to appear in the context in which you've placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you've forgotten to close a previous element. 

One possible cause for this message is that you have attempted to put a block-level element (such as "<p>" or "<table>") inside an inline element (such as "<a>", "<span>", or "<font>"). 

Are they due to Cotonti and how can I validate the skin anyway?

The last straw is, neither Cotonti.com itself passes the validation according to that site.
Look here: W3C Validator run for Cotonti.com