A Cre8asite Forums thread has a typical style question, you find in many forums. A member basically asks, I just made changes to my site, my rankings changed, but is it because of those rankings?
Ammon Johns replies to this thread, so I like to just quote him:
In general, I always say that SEO changes 'mature' over 6 months. The changes I may make to a site this week, will start to have an effect in the first month, but will grow over time as the links effects ripple out, and the overall changes to many pages, to links, and backlinks, filter through the indexing of many many pages. I usually say that full maturity takes 6 months - which includes the extra links that the improvements pick up.
So, the chances are that these are prior changes, even months ago, finally reaching maturity, plus the standard variations of the SERPs too, where yours will not be the only pages online to have changed.
Often, when you make a change to your site, those changes are not reflected too soon. It really depends on the type of change.
If you have an old site that has tons of links to it but all the title tags read "Company Name" and then you change the title tags and fine tune the content to be more keyword specific - then you can expect drastic changes within a few weeks (long sentence, sorry, a bit tired). But if you are constantly making tweaks here and there, it is hard to tell which tweak is to *blame* for the search engine ranking changes.
In most cases, it is hard to isolate all the ranking variables to make a determination on what variable made the difference.
Forum discussion at Cre8asite Forums.