Website Hacked

My website https://www.traversantiques.com now has a link in the header for Viagra “ordine kamarga in linea” which strangely links to a Catholic School!
This ONLY seem to appear when viewing in Internet Explorer for some reason.
I have had a quick look in the header files but not to certain what to look for.
My friend may be able to help but not for a least a week. So ideally I would like to do something myself in the meantime, any ideas would be most appreciated.

Thanks in advance Simon