First, let's look at why you need an HTML Validator in the first place. Ever wanted to see how many HTML “bugs” are on each page of your site at a glance? Now, while each page may be operating just fine, there are some issues with browser compatibility that have plagued developers ever since the days of Netscape versus Internet Explorer. Each company saw the standard HTML guidelines, developed a browser for it, and made their own neat additions to the development of HTML.