If you are serious about your website, you can not just settle with what you see, remember your visitors are worldwide, and they use different screens to access your site – they even use their LCD TV(50 inches). Validation of a website is important as it ensures to the norms and standards implied. The following are the must have validations that you should insist your website developer to check. Validation also ensures more diversed visitors with different setups.
1.W3C Markup Validation Service
3.W3C CSS Validation Service
4. Link checker
5. Mobile compliance
Believe this, it’s worth spending those extra hours and money. !