One thing I admire about Google is their ability to keep track of individual page ranks. What I mean is that EVERY single page has a page rank on your website.

For example my
www.andrewooi.com/about
and
www.andrewooi.com/sitemap

.. are 2 separate pages with their own page rank. Of course with a new site like mine they are all PR 0 at the moment. However over time certain pages on this site will acquire new page ranks and each of this page can effect the site overall page rank as you link between your own pages.

Google likes fresh content so going back to your old posts and refreshing them is a good idea. Every refresh will attract GoogleBot to reindex that particular page no matter how old it is.

What to ‘refresh’ ?

1. Facts
Some facts in old posts can become outdated over time so you can correct them with new facts.

2. Grammar and spelling
You can recheck the whole post for grammar and spelling mistake. One short cut I use is to cut and paste my article into Microsoft Word and look for the green and red squiggly lines.

3. Add links
Since you have new posts on your website, there are opportunities to create new links from your old posts to relevant new posts. The opposite is true also. After reading your old post you may discover that there are new posts that can link to the old one. This mesh of links is good and increase the likelyhood of search spiders indexing deeper into your website.

4. Mark old posts as old
Sometimes the facts in the old posts are so outdated you want to delete it. A better solution is to leave the whole post there but mark it with some warning text saying that certain portions of it is already outdated.