Wow chicos... se pasaron... realmente muy agradecido...
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
con eso arreglé casi todo .. igual tenía una mezcla entre xhtml y html 4.01... no tenia idea la verdad.. es primera vez que valido la página...
ahora solo tengo un error y ni un warning... el resto los arreglé todos... este es el error que queda:
This page is not Valid XHTML 1.0 Transitional! Result:Failed validation, 1 Error Server:Mozilla/5.0 (Windows; U; Windows NT 5.1; es-ES; rv:1.8.1.9) Gecko/20071025 Firefox/2.0.0.9
Size:(undefined)
Content-Type:text/html
Encoding:iso-8859-1
Doctype:XHTML 1.0 Transitional
Root Element:html
Root Namespace:http://www.w3.org/1999/xhtml
Line 66, Column 21: there is no attribute "onClick".
<button onClick=
"fajax()" type="button" class="btnform">Publicar</button></
You have used the attribute named above in your document, but the document type you are using does not support that attribute for this element. This error is often caused by incorrect use of the "Strict" document type with a document that uses frames (e.g. you must use the "Transitional" document type to get the "target" attribute), or by using vendor proprietary extensions such as "marginheight" (this is usually fixed by using CSS to achieve the desired effect instead).
This error may also result if the element itself is not supported in the document type you are using, as an undefined element will have no supported attributes; in this case, see the element-undefined error message for further information.
How to fix: check the spelling and case of the element and attribute, (Remember XHTML is all lower-case) and/or check that they are both allowed in the chosen document type, and/or use CSS instead of this attribute. If you received this error when using the <embed> element to incorporate flash media in a Web page, see the FAQ item on valid flash.
Ese es el error que queda... trate cambiando a estrict, pero me da el mismo error... alguna idea??? y muchas gracias