How to delete specific HTTP authentication credentials from Safari (for Windows)?

Manage Your Passwords

Step 1: Go to the 'AutoFill' section in the Safari Preferences window.

Step 2: Click on the 'Edit' button to the right of where it says 'User Names and Passwords.' This will bring up a window displaying all of the passwords and usernames that you have authorized Safari to save.

Step 3: Click on a password listing and push the 'Remove' button in order to delete the password from Safari's memory.

Step 4: Choose 'Remove All' in order to delete all of the saved passwords.

Step 5: Manage your passwords as you see fit.

Source : http://www.answerbag.com/articles/How-to-Manage-Passwords-With-Safari/f6de5c02-c6e6-0f2c-5f27-197a996ebced

If you are on Mac OS X and you are wondering how to remove a basic-authentication credential from a website, you won't find the password in Safari preferences. The answer is in the Keychain Access App. Open it up (it's in Utilities) and then go to the Passwords Category (the categories are on the left, at the bottom - you don't need to be doing anything with your keychains here). Search for the name you want to get rid of (it will be something like "your.internetserver.com (john.doe)", select it, right click, and then delete it.

You should be able to make Safari prompt for credentials again by explicitly specifying wrong credentials:

http://foo:bar@yourintranetserver/

This assuming your actual user and password aren't actually "foo" and "bar".

You can save it as bookmark calling it "reset intranet credentials".

This reminds me that I can temporary change my auth credential in Chrome by using Incognito mode (private browsing). -- FYI