If you are accessing iShare GIS from a computer that is not in a Windows domain trusted by the server running the iShare GIS front-end then you may see a prompt for user credentials.
MS Internet Explorer
If this is happening and you are using Internet Explorer, it is probably because Internet Explorer thinks you are not on an intranet because the host name contains full stops. To get around this problem, go to Tools -> Internet Options -> Security tab then click on Local Intranet then press the 'Sites' button. This will allow you to add the host of the intranet site to intranet zones e.g.
Mozilla Firefox
In Firefox, things are slightly different. Firefox will not authenticate with any site that has NT Integrated authentication by default, whether there is a full stop in the host or not. See the following link for instructions:
http://markmonica.com/2007/11/20/firefox-and-integrated-windows-authentication/