You can write an application configuration file for your simple web browser, in which you can store these credentials in XML format
<defaultconnect>
<user>admin</user>
<password>admin</password>
<address>192.168.1.1</address>
<defaultconnect>
</defaultconnect></defaultconnect>
On Application_Start method, you fetch these details using C# ConfigurationManager class
foreach (string key in ConfigurationManager.AppSettings)
string value = ConfigurationManager.AppSettings[key];
Then apply in the default connectivity code.