I mean to say is do they update every day!! As yestarday i got my site to the 26th position for a keyword and today it has jumped to 21st position. So i am a bit confused
Google SERP updates are constant and unrelenting. Unlike their PR updates which appear to be sporadic and lacking.
Serp changes all the time... unlike 'published' PR which is only made public every 3 months... or is it 4 now?.. or 5?
I think there was a major change, but I need to wait 2-5 more days to see exactly. I lost a lot of traffic 2 weeks ago, but yesterday all seemed normal again... Hope it's good again.
I see on at least 10 of my sites Google SERP fluctuate every few days. Can be dramatic like a page no where then in top 10 or it just can be moving a few positions. From what I can see, these fluctuations seem to be something to so with link popularity which i can see on very competitive keywords. As people build more links all the time this seems to affect the rankings on a near daily basis. Additionally penalties can come in and have a large negative effect on rankings at any point in time.
Track your keywords using Digital Point's Keyword Tracker. You'll see lots of keywords changing in the SERPs every day, sometimes more than once per day.
Have a read of Matt Cutts post Explaining algorithm updates and data refreshes which explains a bit about the process. Another factor that he doesn't mention as it's alot newer is the QDF or Query Deserves Freshness factor. If your site is in a newsworthy niche there can be larger swings because QDF means a new page may be way more relevant to the query then a solid 5yo PR7 page. You can use it to your advantage, say you have a static wallpaper site on Madonna.. If she gets arrested or hits the press for something, throw up a page about it then entice them in to your older content.