Sorry, this site hasn't been shared with you.
Just a page with this rather curt message and nothing else. No ribbon; no user welcome menu thingy; nothing. Hmmm.
Answer: use the URL http://site.domain.com/_layouts/closeConnection.aspx?loginasanotheruser=true. This should get you to the login prompt and you can then change user. No need to restart the browser or fiddle with the stored credentials settings in Control Panel.
Just one caveat: this option uses an unsupported browser feature which is potentially unreliable and apparently does not work in IE 10 and Safari. In this case an alternative is to start the browser with different credentials using the "Run as different user" context menu option which you can see if you hold down the shift key while right clicking the browser link. Another option is to find your credentials cache through control panel and remove the item.