going down in the serps

[caterfix]

Hey all, i am reletively new to webmastery but my site is (so i have been told by SEO pro's and webmaster friends) prety well optimised. I change the text etc around and ALWAYS focus on my 3 keywords that i wish to rank highly for...The sites only been up for around 4 months now as it went down for a while . However, from nowhere to now i have got it to the 2nd page of google for "used catering equipment" and even the first page for google for "used catering" and "used catering supplies". This is obviously prety good, but the keywords i want (used catering equipment) to be high are constantly moving up then down the next day...i know this is meant to happen but when it moves down you have to think why?...

Any help would be greatly appreciated!!

[surreypcsupport]

You get different results from different results centres. In addition all the other sites ranking for those keywords may also be changing their content/building backlinks. And new pages may appear above you.

Also consider Click Thru Rates from SERPs. These affect your rankings too so as you get to page 1 or 2 of the listings all sites are more likely to be clicked on. This makes CTR more important on these first two pages. If other sites are getting better CTR than you through more enticing page descriptions/titles then you may lose positions.