Hi Kdollar
You ought to hang around http://www.webmasterworld.com – all the answers are there. Now sorry if i am about to teach you to suck eggs, but…
Essentially there is an ageing factor applied to some sites by some engines along with an “importance” factor which may also be relevant to Altavista. Linking is a key attribute here…get quality inbound links and some engines view this as a testimonial.
Its not quite as straightforward as that obviously. There are many other factors – content, keyword density, html formatting, outbound links, size of site and pages, competitive analysis – loads of stuff. The above site will help you immensely to understand the differences, though its impossible to get it 100% right due to the secrecy of search engine algorithms.
Cheers
Simmo!