I've managed to optimized one of my websites to rank 2nd on the first page for the search term I wanted it to rank well for and quite often I go and check to see if the rankings are still the same or if they have changed.
Yesterday I went to check and I see my website's not even on the first page! I thought that was odd, so I decided to do a quick search via both my mobile phones and my website is ranking normally (2nd on the 1st page).
So why is it that when I use 2 different mobile phones to do the search, my website is there and ranked normally as expected whereas on my desktop pc, my website has dropped off the first page (disappeared)?
WTF is going on? This doesn't make any sense! The only difference I can think of between my mobile phones and desktop PC is their IP address but how could that possibly effect rankings?
Just so you know, I don't do any dodgy backlinking strategies. In fact I don't even do any backlinking strategies to begin with!
** UPDATE **
So I quickly did a search on my desktop PC now and suddenly my website re-appeared back to 2nd on the first page. I then refreshed the google search and my website has disappeared again!!
There has been two recent Google updates, Panda 4.1 targeting thin and low quality content, and some updates fighting private blog networks (PBNs).
If you have content quality issues, fix them and it will help with rankings. If you benefit from backlinks from PBNs, remove them or disavow them A.S.A.P.
As usual, every updates often provokes the Google Dance (link to personal post). This could explain what you are observing too.
REM: Since this question is SEO related it should be posted in Pro Webmaster (at least you know for next time).