Actually, I do! I recently came across a great article on writing valid HTML and if it actually matters in web development. The author makes a great point that it’s usually not necessary as long as your pages display correctly to the viewer. Validating your code can also be very time consuming and impractical especially when your building a large web application. As soon as you start including various scripts and programming languages the amount of errors usually goes through the roof.

On the other hand, as a web designer/developer who tries to write clean semantic markup, having Valid HTML and CSS is way for me to show of my web development chops. Another reason to validate your code is to ensure consistency between browsers. For instance, Firefox is far more forgiving than say Internet Explorer or even Safari. For further reading make sure and check out Coding Horrors article HTML Validation: Does It Matter?