Bookmarklet to validate local file with W3C by RobW (http://stackoverflow.com/u/938089)

validationbookmarklet

javascript:(function(){function c(a,b){var c=document.createElement("textarea");c.name=a;c.value=b;d.appendChild(c)}var e=function(a){for(var b="",a=a.firstChild;a;){switch(a.nodeType){case Node.ELEMENT_NODE:b+=a.outerHTML;break;case Node.TEXT_NODE:b+=a.nodeValue;break;case Node.CDATA_SECTION_NODE:b+="<![CDATA["+a.nodeValue+"]]\>";break;case Node.COMMENT_NODE:b+="<\!--"+a.nodeValue+"--\>";break;case Node.DOCUMENT_TYPE_NODE:b+="<!DOCTYPE "+a.name+(a.publicId?' PUBLIC "'+a.publicId+'"':"")+(!a.publicId&&a.systemId? " SYSTEM":"")+(a.systemId?' "'+a.systemId+'"':"")+">\n"}a=a.nextSibling}return b}(document),d=document.createElement("form");d.method="POST";d.action="http://validator.w3.org/check";d.enctype="multipart/form-data";d.target="_blank";c("fragment",e);c("doctype","HTML5");c("group","0");document.body.appendChild(d);d.submit()})();