A co-worker asked me today about an issue in a Web app in which pages display correctly in IE 6.0 but incorrectly in IE 5.5. He could duplicate the problem in IE 6.0 by changing the page’s <DOCTYPE> tag. Sometimes issues like this are due to rendering engine differences (or bugs) in various browsers. However, I very often see developers test the code and functionality of their Web pages, but fail to test the HTML.
There are far too many Web pages out there that have broken and/or sloppy HTML. I know, I know, you have a deadline to meet and as long as it works on your computer it’s fine, right? Hopefully that’s not your attitude. There’s an excellent, free tool from the W3C that can quickly and easily validate your HTML and give you a list of errors and issues. You can quickly jump to the trouble spots and make corrections.
The W3C (World Wide Web Consortium)’s free Markup Validation Service can validate HTML, XHTML, MathML, SMIL and SVG documents, and it is still being tweaked and improved. I highly encourage you to add it to your Web development toolkit.
