Well, maybe not that strong but the argument for having standards compliant code on your site is now backed up withÂ crawl data from Google.
Courtesy of search engine land there is now graphical evidence showing that Google is able to crawl more pages and also crawl deeper on a site that complies with the HTML, CSS and XML standards from W3C.
Standards compliance should always be adhered to; not just from the point of view of enabling search engines to access pages with ease but also because is allows much easier upgrade paths, cross browser compliance and has on page performance benefits. Of course it is much more pleasing to view clean, concise, correctly indented code than a mash up of bad formatting with little or no attention to detail.
Key things to try ensure when creating new pages are:
1. Removing inline script and placing in external code files
2. Removing inline and embedded CSS and placing in external files
3. Closing tags (if using XHTML as your document definition)
4. Ensure the correct attributes exist on your HTML elements
5. Use classes and not inline style attributes
All small things but tackling each one, one step at a time, will make the internet (and therefore the world) a better place.