Hi,

Here is the answer,

It's the process by which we check files - html, css and other things - to see if they comply with industry standards. For some, the process of validation gets in the way as they create web content. That's a fairly dangerous attitude.

Integrate validation into your creative process. Once that becomes part of the way you do things, you'll thank me for it. As I like to say, "Validate early and often."

There are three real good reasons why you want to validate your work. Each of them support the principle of adherence to specifications.

1. It Helps Resolve Cross-Browser, Cross-Platform And Future Compatibility Issues.

By creating files that are syntactically correct, you stand the highest probability that your page will work properly in the greatest number of devices, software and operating systems available today or emerging tomorrow. Using the most widely supported industry standards is a method of safeguarding your designs against future shock.

2. Search Engine Visibility

Creating well-formed documents means using syntax that search engines, like Google, love. Without getting too techy here, search engine spiders crawl through web sites and index your pages so that others may find you.

3. It's A Learning Tool

Once you starting validating your files you'll find the process to be an invaluable learning experience. Validation itself will teach you what are the best ways to create your XHTML/HTML and CSS files. Validation is a great teacher.

Thanks.