Scenario: Lets say, right now I am logging the SharePoint site with SP1 user’s credential but I need to test the site for SP2 user’s also. So for this I have to first Sign Out from SP1’s account then again Sign In with SP2 user’s credential. But we can do it easily by enabling “Sign in as Different User” option in the browser.
To enable “Sign in as Different User” paste below code to Welcome.ascx page at “C:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\TEMPLATE\CONTROLTEMPLATES” (here C:\ is my root directory for SharePoint)
<SharePoint:MenuItemTemplate runat="server" id="ID_LoginAsDifferentUser" Text="<%$Resources:wss,personalactions_loginasdifferentuser%>" Description="<%$Resources:wss,personalactions_loginasdifferentuserdescription%>" MenuGroupId="100" UseShortId="true" Sequence="100" />