The problem with "Sign In" is that it reads a lot like "Sign Up" (another common web site expression). Consumers should be accustomed to Log In and Log Out (e.

The problem with "Sign In" is that it reads a lot like "Sign Up" (another common web site expression). Consumers should be accustomed to Log In and Log Out (e.g. on Mac OS X the Apple menu says "Log Out [user name]..." and the user menu has a "Login Window" item).