Google changes since Oct/03: What do we know for sure?

how has google's ranking method changed since Oct/03?

[adla111]

In Oct/03, a few sites of ours which had listed in the top 3 for the past few years disappeared from Google. The sites have bounced around since then, and some are doing reasonably well again (on the second or third page of SERP). We have not made any changes whatsoever to the website since Oct/03.

As of now (Mar/04) have there been any firm conclusions as to what changes Google has made in how they rank webpages?

Obviously there has been loads of speculation, suggestions, and opinions about this. But is there anything we know for sure now? Or, at least, anything that most people are agreeing on as to what factors have become MORE important, and what factors have become LESS important regarding Google's method of ranking webpages?