Does it help SEO if we use a valid HTML? Example using <br /> instead of <br> or using <meta name='blah blah' content='blah' /> instead of <meta name='blah blah' content='blah'>
Many of the #1 SERPs pages will not pass HTML validation. Google does not require it. I just do it because it is good design.
Yeah I doubt any search engine would take the time and resources to examine the validity of each page's html code. It is more to help your visitors by keeping the page looking consistent on any browser. Plus it can help prevent roadblocks for search engine spiders. Even though it won't help seo, I would still recommend doing it. I don't close each tag with a forward slash though. I don't remember that ever being a part of valid html.
not necessarily shorter, they just add up trailing slashes because it would be a sign for single tags in XHTML.
You should definitely use valid html. Google bot and other search engine bots are just programs, and it's possible that broken html could mean the bot would fail to index your website properly. Why take the risk? I am sure they have all sorts of inbuilt code to recover from errors if they do find bad html, but it makes sense anyway I think to keep all your code valid. Cheers
with regards with ranking HTML Validation (according to W3C standards) of a page "it cant help. or less important "
Look guys valid HTML & CSS is definitely helps to your seo work and your visitors as well and if your site is looking good and clean then visitors will remember your site and bookmark as well in short it will showing good impression to your visitors. And I'm always yousing <strong> tag here little bit difference between <b> tag and <strong> tag. <Strong> tag spot all the browser and showing same as it is. <b> tag not spot to all the browser and some time it showing different - different result.
HTML validations identify the errors in your pages that can act as faltering blocks for spiders. Rectify these errors will help increase your site's ranking on serp.