This parameter identifies the page a user was on when an event occurred.
For example, when a user clicks on a link, the event source shows what page the user was viewing when the click occurred. Although in the case of a page view, these URLs are identical, in the case of a click the dcsuri is actually the “destination URL” of the click, while the event source is the “source URL” of the click.
WT . es = <hostname>|<page>