Web Page Size for SEO purpose

How much a size of your web page affects your website ranking? I see that most of the web pages that appear in top of search engine have a very small size.

For example if your competitor web page size is 15KB and your web page size on the same keyword is 50Kb then there is more chance that your competitor will rank better than you because search engine crawlers like small and error free pages.

According to W3 Validator and Wikipedia that less than 20% of the major search engine and browser websites are validated and error free.Please make your webpage size less than 120kb.

Let one thing I want to clear you that page size means enough coding not content.