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Thanks for the quick reply, it's much appreciated. I had guessed that it wouldn't be a major issue, but wanted to be a bit more certain before going ahead with the WordPress site for the client.

The errors certainly don't have a negative effect on the sites' layout, content, usability or load times. From what I can tell they are due to the theme making use of iframes and video embeds in a non-standard manner. The rest of the HTML is sound. As you also mentioned, it does seem to be related to the theme the client wants to use, as with other themes I can get valid HTML code output.

Hi all, I'm new to SEOmoz and SEO in general really. I run a small but well regarded freelance website and graphic design business, and until very recently had an employee who handled the SEO side of things. I'm now looking to step into this role myself and hopefully learn the in's and out's of SEO. I've no doubt there will be much to learn, but the SEOmoz tools and it's community seem excellent and helpful.

My question then is basically, if WordPress generated HTML code can have an effect on SEO, when it's reported as invalid by tools such as the W3C HTML validator?

I'm used to hand coding the majority of my websites for clients, where creating valid HTML and CSS code is something I can do with relative ease. A new client however wants to use WordPress - for ease of updating the site content themselves. The client does however consider any potential SEO implications to be a very important factor in choosing a hand coded vs. WordPress based website.

I am aware that WordPress itself is just a means of generating HTML code, and that to the search engines there is no difference between this and the hand coded websites I usually produce. However if WordPress is generating HTML that is being reported as invalid, would this make the search engines penalise the site?

On a second note, will the search engines look negatively on a WordPress site where it is being used as a standard website, and the content may not be updated as frequently, as say, a blog?

Thanks for your time, and I look forward to hearing your suggestions.