A URL such as http://username:password@example.com/ does not work in Internet Explorer, as explained in the Microsoft Knowledgebase article “Internet Explorer d
Per the Knowledgebase article, this can be enabled by setting the DWORD for iexplore.exe to 0 in:
[HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_HTTP_USERNAME_PASSWORD_DISABLE].
Doing so will enable you to browse to URLs using the syntax [user]:[password]@[url].