Alert Boxes

This JavaScript program just put up three alert boxes.

• The first alert box had an undefined message. Usually you WANT TO AVOID this. In Netscape Navigator version 4, look carefully at this alert box so you can detect and fix this problem when it occurs in the future. (In Microsoft Internet Explorer, Mozilla and Netscape 6.0 you can't tell, which illustrates the fact that different browsers sometimes behave differently. Always test your code on several different browsers.)
• The second alert box had a blank message. This was just a curiosity.
• The third alert box illustrated warning the user of a possible bad situation. It contained a SAMPLE WARNING MESSAGE: Possible data error message.