I am looking into some html provided by an advertiser that we would like to link to, and it has a strange image included at the end of the html code:
<img src="http://www.<some domain>.com/image-<some numbers>-<some numbers>" width="1" height="1" border="0"/>
What is the point of this? Is this to count impressions?
Additionally, those "numbers" may represent unique data like affiliate ID or may be unique to your site. So, when a browser requests the image, the server may set a tracking cookie that gets your site or the affiliate paid for any eventual purchases on the advertiser's site.
This is totally harmeless at worst and could be profitable at best.