4 Reasons to Validate your HTML (01 Jan 1998)
HTML validation allows authors to check their HTML syntax. Valid HTML is less likely to cause problems with different browsers and more likely to survive the next browser release. There are many reasons to validate your HTML, but here we have chosen to focus on historical examples that show why visually checking your Web pages in browsers is not enough.
Article URL: http://www.htmlhelp.com/tools/validator/reasons.html