External Style Sheets are a must for fast loading well designed flexible websites.
When I get a new webmaster as a client the first thing I suggest to them is to allow me to switch their site over to using a cascading style sheet (or CSS for short).
There are a thousand reasons for this, beyond loading faster and taking up less resources,it makes the page less cluttered with tags and font styles and allows the search engine spiders to really cruise through a site.
The page you are looking at right now is a table less CSS designed website that loads fast and is geared just towards making the search engines happy from a technical view point.
Now you might not think that page size matters much to search engines, but remember to get to your internal links, they have to "read" your whole site to find them. If your page is smaller they can do more crawling before the resources they have allocated for your site are exhausted.
Style sheets and clean code are a must for good readability and keeping the
search engines happy.