American Express card holders: <A HREF="http://news.yahoo.com/s/zd/20060428/tc_zd/176969">beware that pop-up log-in screen,</A> even on the company's secure Web site. The credit card and travel services company has issued a warning about what it calls a false "security measures" pop-up screen that appears when users log in to its secure site. In an alert posted online, the New York-based company included a screenshot of the pop-up, which tries to lure the user into entering name, social security number, mother's maiden name and date of birth.