This is the code I currently use:
<% Uri MyUrl = Request.UrlReferrer;
if( MyUrl != null)
Response.Write("<a href=\"" + MyUrl.PathAndQuery + "\">Back</a>"); %>
I would think there is a more "MVC Html helper" way to do a "Back" button. This may require more information about the routes already setup, a list of possible parameters, etc. but I don't want to assume this is the case. Maybe there is some way to match the url to the defined routes like in the manner a regular expression works?