Trojan warning on Facebook.?

[madjax]

Can access signing in on FB but after putting password etc Avast immediately tells me there is a trojan threat but has been blocked. Then anything else I press within FB just gives me the same warning. It's happening if I use Chrome or Firefox but Hotmail & Yahoo don't appear to be affected. Seems the problem is on FB but how do I get rid of it please?? Thanking you in advance.

[Bronwyn]

it's a virus in your facebook you can't sign on until facebook fixes it