Extraneous advertising on the site

On my site, in his cap, constantly appears advertising, which I did not place. These are advertising banners. I don't know what to do anymore. Help me, please, get rid of someone else's advertising on the site. For example: www.ozeroskazok.com/stcenarii-skazki/novye-stcenarii.html . This advertisement is displayed on all pages except the main one.Please help me. I can't do it myself.

Yeah, I just turned it on the malware scanner configured to analyze the entire filesystem. 20 suspicious files. I don't know what to do with them.

I just sent the data.