Old school HTML and rankings

[DavidWilsonSEO]

How does really old school HTML (with inline CSS and a boat load of markup errors) affect modern SEO?

I'm talking purely rankings, not conversions or bounce rate etc.

[tomcraig86]

All websites render in HTML and CSS, regardless of what they are programmed in!

In terms of site structure, it may be easier to have issues with Canonical URLs, broken links, missing redirects etc, as these sites are unlikely to have any form of Content Management Systems.

Be careful with inline CSS and Scripts, as these can dilute your actual meaningful markup in your files and give a bad content:code ratio.

In reality, there is no reason that a completely flat HTML website could not rank number 1 for the most competitive term in your niche

[DavidWilsonSEO]

Yes, the problem is that it is not flat HTML.

I think that the site was originally a flat HTML site, with inline CSS (and JavaScript on page) that was added into a CMS (which isn't the best CMS for SEO, in my opinion).

Personally, I think flat HTML (coded in modern markup) sites are better to work with on the small scale due to the amount of flexibility they offer. Actual HTML sites are not my real issue, my issue is the unclean code.

It is way beyond current standards, there are bits of Java in there that don't do anything and the code is very long for the size of the page and the amount of content on there.

My question basically is, would two sites with identical content (ignoring the issue of duplication for the purposes of this hypothetical), rank differently if one had new, clean and error free code and one was the original with the errors and the out of date code?