Google has made five significant changes to its algorithmic formulas in the last two weeks.
1. Increase in Index Size - Google's spider, Googlebot, has had a busy few weeks -- at the time of the update, Google announced that it had massively increased the size of its index.
2. Latent Semantic Indexing (LSI) - This is a very significant new technology that Google has always been interested in, and the incorporation of LSI has been on the cards for some time. In short, LSI is about using close semantic matches to put your page into the correct topical context ...It's all about synonyms.
3. Links and Anchor Text - Links have always been the essence of Google, but the engine is steadily altering its focus.
4. Neighbourhoods - Now, more than ever, has the question of who's linking to your site become critical. Links must be from related topic sites (the higher the PR the better); those links are seen to define your 'neighbourhood'.
5. Downgrading of Traditional Tag-Based Optimisation - Clever use of the title, h1, h2, bold, and italics tags, and CSS, is no longer as important to a site's ranking as it once was.
