How is this html code getting into my webpage without me doing it?

I'm not putting this code on my page and when I delete it, it shows up again on my comcast home page? Has someone hacked into my account or is this possible to an automated system is somehow appending it? the code is this:

fhposlekorrzfluvzxg… width=605 height=563 src="http://the-previous-life.ru:8080/in… >

which an .ru page is russian federation. I want to know how it's getting on my personal page and how to prevent it.