After a few minutes on a minecraft server it shows the picture and I don't know what to do please help.

Does this happen to any other players on the server, or does this happen on multiple servers?

I also found this:
http://www.minecraftforum.net/forums/support/unmodified-minecraft-client/1865758-ioexception-an-existing-connection-was-forcibly

It could be a corrupted chunk.

Happens on multiple servers and I don't know if it happens to other people.