These two sources allow you to check to see if your website is compliant with HTML, XHTLM or CSS standards. HTML validators operate by comparing the mark-up on a web page to the W3C standards. The standards vary depending upon the declared version and so the validator will start by reading the “doctype” declaration to see which set of standards to apply. Once the validator has read the page and determined the applicable standards it looks for such things as missing opening or closing tags, missing quotation marks and other hand-coding errors. So if you have been looking for hours to find what’s wrong with your code, try one of these websites.