Newbie Question Regarding Google's Page Rank

After finding a site on BHW that sells backlinks, I decided to try it out. I don't really feel it's effective, but nonetheless it's getting the name of the company I'm promoting out there.

Here's the weird part.. when I searched a term on Google, the company website popped up 4th and I was immediately happy. 5 minutes later, I checked again and it was on the 4th page of Google.. wtf happened? It never went back on being 4th on front page.. it just continued to stay on the 4th page of search results..

Anyways, thanks for all your help BHW

Were you logged in to your google account when you checked? Sometimes being logged in changes the rankings if you've searched it before.

Possible what ^^ said or it could be Google Dance.

P.s. It should be called SERPs. Page Rank is different thing.