SEO & Validation

There's a great deal to be said about the merits of validation, much of it often overlooked. Validation will generally give you cleaner, faster, quicker-downloading pages that the search engines will love. If a page is validated, an engine can perfectly well understand the contents without needing to be convinced by the anchor text of innumerable inbound links. There's a growing body of evidence to suggest that pages that correctly validate will rank higher than similar pages that don't. I can and do use a validator to check syntax. This isn't just being picky, it's entirely possible for an engine to fail to appropriately index a page if indexable content is not recognised as such due to coding errors. It's a shame if you've hired in an experienced (and expensive) copywriter to ingeniously shoehorn keywords into a sparkling piece of theme-laden prose which gets missed by the engines because of some obscure coding typo. It's always best that the engines are able to determine that your pages are indeed dedicated to their intended subject and are not about tables (an html term) of improbably small size.
And don't think it doesn't happen!

Web sites generated by WYSIWYG (What You See Is What You Get) editors will typically have a great deal of superfluous code on every page. That means that each and every page takes longer to download and appear on screen than it otherwise might.

Properly validated, faster loading pages make it easier for your clients to access your online store and find the goods they want to buy.

I use TIDY and two of the CSE validators to check syntax. I use two as one of them is a Lite version. I'm regularly presented with pages that the world and its dog have been working on and there's sometimes very little apparent rhyme or reason to the coding. In cases like that, often the standard CSE validator will choke on the pages and give up. So does Tidy. By contrast, the Lite CSE validator, ignoring as it does most of the errors, will point out only a handful compared to the others. Often, fixing these few will sort out the majority of the rest, leaving me with a much easier job.