How can I tell what site my end users are coming from?
Tracking referring URLs for customers visiting your Customer Portal
Analytics, End-User Pages
To determine the site your end-user came from you can look at standard report ID 163, "Referring Sites". This will show you the sites that people are coming to you from based on percentage. This is a percentage of all traffic over the last 30 days.
When using the Clickstreams data, please keep in mind that there is only limited data available from the last 30 days. Because of this you will not be able to report on data older than 30 days.