Typically this is used by external code widgets which post the current url to an external site - such as Facebook, Twitter or Browsealoud.
Older styles may use code which references:
<%=CurrentRequest.Domain %><%=CurrentPagePath %>
These methods are outdated and will cause the page to error and not load correctly in Easysite 7.
In Easysite 7 this code should be replaced by:
<%=RequestContext.Url.Host %><%=RequestContext.Url.AbsolutePath %>
