Hi Leeky,
no need to register a subdomain, TradeDoubler will track all clicks from any subdomain or folder as long as you have registered the top level domain under "SETTINGS>>Site Information".
You can register multiple URLs per site simply by placing a comma, and no space, after each URL, e.g.
http://www.site1.com,http://www.site2.com.
The following are examples of a banner and top products being encoded with the EPI parameter:
Code for Top Products Banner, including EPI:
<script language="JavaScript" src="http://impgb.tradedoubler.com/imp/1059251/913664[blue-widget]" charset="ISO-8859-1"></script>
Code for Standard Banner, including EPI:
<script language="JavaScript" src="http://impgb.tradedoubler.com/imp/1059240/913664[blue-widget]" charset="ISO-8859-1"></script>
When you are adding the EPI code to banners you need to place the EPI parameter in square brackets.
Before EPI:
<script language="JavaScript" src="http://impgb.tradedoubler.com/imp/1059240/913664" charset="ISO-8859-1"></script>
After EPI:
<script language="JavaScript" src="http://impgb.tradedoubler.com/imp/1059240/913664
[blue-widget]" charset="ISO-8859-1"></script>
The above EPI encoding, in conjunction with your TradeDoubler "Keyword Report" will allow you to calculate the ROI for each landing page.
Thanks,
Nick