To access the parameters passed to a HTML page that a Silverlight application is embedded in, you should use the QueryString method of the HTMLPage.Document class. For example, if the HTML Page URL is 'http://www.dummysite.com?username=myuser' you can access the username parameter as follows:

string username = HtmlPage.Document.QueryString["username"];

The value 'myuser' will be assigned to the above string. You must also import the following library to access the HTMLPage:

using System.Windows.WebBrowser;

For details on accessing parameters from within a HTML Page see http://tinyurl.com/786r4c.