Create account form in monobook skin using SimpleCaptcha
SimpleCaptcha doesn't set an input field size, so it defaults to 20 wide. Monobook puts the captcha div in a big white box and as a result the field wraps onto a new line in the new login and create account forms. See screenshot.
The fix is trivial and similar to bug 47763 in which we reduced the size of the FancyCaptcha input field.