When logging onto or downloading any files in SharePoint you will be prompted to enter a Username and Password.
Follow the steps below to add your SharePoint site to the local intranet zone of Internet Explorer and avoid this annoyance.
Open your SharePoint site e.g. yoursite.com:987
Select Tools then Internet Options in Internet Explorer
From the pop up window select the Security tab then Local intranet and click the Sites button
Click the Advanced button
Click the Add button which will add the SharePoint URL to your trusted local intranet sites.