To open a mail message from a textbox you can use the following URL in the action box of the text.
To open a webpage in a new page
In the report viewer there is no back button which will take tyou back to your original report. What you can do is create your own textbox which you use the action function to take you back to the main report. This refreshes the original report, you can use the following URL and this will take you back to the main report whithout refereshing it.