How long it takes Google to download one of your pages is now a major ranking factor. Think about it, if it takes Google 5.5 seconds to download your 800Kb badly optimised webpage, then it can only crawl so many pages before you hit your limit of what Google will download from your site.
Websites like bbc.co.uk have a nearly constant flood of new articles, with millions of people viewing those pages each and every day. The BBC's website has built up a great reputation and Google knows this, therefore giving their site a higher data download level.
Good SEO Requires Fast Load Times
Your site needs to be optimisaed for as an efficient data download level as possible. Ask most web designers or SEO experts what expires headers are? or how to add image caching with htaccess? and you will get a blank look back from them.
Do you have:
- Properly sized images
- Valid html
- Site wide gzipping
- Expires headers set
- As few CSS files as possible
These are the types of system settings and site configuration that is now a major part of SEO.