If you are of the opinion that having the cleanest web site on this world can get your site ranked high on Google then please drop this thought at least at this moment. Having valid HTML and error free codes really helps to enhance the user experience but does not count as a ranking factor for Google. Although, it is suggested to have valid HTML on your site and in future it may get counted by Google.
Have a look at the video by Matt Cutts in which he discusses does Googlebot cares about valid HTML?
Also See:-
Advertorial Link Building Spam
Syndication is a Valid Way to Get Links
Google Pushes for User Sharing of Sites
Where to link to the original source in the article?
Links from article marketing sites
Importance of Backlinks in Seo
How to Create Backlinks That Google Loves
How to Rank in Google
Google Search Quality Updates
