Why Has My Site's Home Page Disappeared? It was no. 1?

[Truegho]

I was very annoyed to see that my site's index page has dropped from the No. 1 position on Google Search. Not only that, but the page isn't even appearing on any of the other Google search pages. This is VERY worrying, as I am losing Adsense earnings due to the sharp drop in traffic. This drop occurred from around Mid- May 2009, and I was just wondering if any other webmasters have experienced a similar problem.

I can't even find Google Support, as all I am getting are their General Help pages.

Somebody PLEASE advise me on what has gone wrong here, as my site was formerly the most popu8lar site in its subject on Google search,

[tedster]

Do you have a Webmaster Tools account? That's the first place to check. You may have a technical issue that obstructs spidering. You may also have some kind of server hack [webmasterworld.com] that you need to take care of.

There are so many possibilities that it's hard to mention them all - but have a look through the Hot Topics area [webmasterworld.com], which is always pinned to the top of this forum's index page. You may get some ideas that way on what to research.