Is it really necessary to have a competely validated Mark Up and css for SEO purposes

Question

While validating my CSS on http://jigsaw.w3.org/css-validator/

I am getting following errors:

1.Property zoom doesn't exist : 1 1.

2.Property -webkit-transition doesn't exist : all 200ms ease-in all 200ms ease-in

3.Property opacity doesn't exist in CSS level 2.1

4.Property -moz-border-radius doesn't exist

5.Property -webkit-border-radius doesn't exist

Is it really required to validate the MarkUp and CSS completely for SEO or these errors which mostly are browser specific can be ignored for now.

If these errors have to removed can someone please suggest the way to do so also.

Answer 1

CSS errors don't have any effect whatsoever on SEO. HTML errors may have a tiny sliver of effect, but unless your markup is so bad a parser can't take the text out of it (and in that case it probably won't even work in a browser), it won't have any negative effect. Validating is a nice touch from a programming perspective, but in my experience, practicality beats it every time, especially with CSS.

Answer 2

If for whatever reason you need the page to validate (e.g. to keep the client happy) but also need to use non standard properties for your page to work you can do this by adding them dynamically with javascript so the validator doesn't pick them up!

Answer 3

SEO & Importance of Valid Source Code (W3C Validation) @searchenginejournal.com.

This article and comments are both very insightful.