Checking capital characters for password.

One of my favorite web site is We Disk: http://global.wedisk.co.rk
One day I have typed in Captial characters as my password, and the web site showed this pop-up message.
The meaning is that

if your "Caps lock" is turned on, password will be wrong.

I think some of people might intentionally use "Caps lock" when they type in password. But it is good to notice the users all the time.

In addition, I like the simple image that the pop-up message uses. It is instinctive.