There are many website that are not being listed on the search engines. The reason behind this is found that most of the website examined are not HTML validated. No search engines likes to index a particular website that contains non validated HTML codes.

What is HTML Validation:

Validation is the process in which a document is compared to a set of document rules, in this context a DTD, and then a report of rule violations is created. Typically, a document author will submit a draft document to a validation service, use the report to identify errors, correct those errors, and resubmit the document for validation.

Note that validation compares a document only to the syntactical rules of a DTD. There are more general "checker" programs that provide services like spell-checking, link verification, and stylistic tips. None of these programs, however, can check for abuses of the intent of HTML syntax; using

in an attempt to force indentation, for example, is something validators cannot check; whether this should actually be considered invalid HTML is subject to much debate.

Validation Tools:

There are many online validation tools available online through which one can check the website design for HTML validations. All one needs to do is submit the URL of the website design and the validator will check for the HTML codes and shows results accordingly.

Apart from that a few service providers like yahoo also provides users with the option of website check for HTML validations.

It is important to check the website design through HTML validator so that the webpages of the website design should be error free.