Yahoo Messenger (formerly known as Yahoo Pager) is a free service that allows you to see when friends come online and send them instant messages. It can also alert you to new e-mail in your Yahoo Mail or Yahoo Personals account, or when you have upcoming events recorded in Yahoo Calendar. Yahoo Messenger offers firewall support, a standby mode that minimizes the program until an Internet connection is made, the ability to save and print your conversations, and a tabbed interface that provides quick access to your favorite stocks, news, and sports scores. Other features include the ability to create a chat room automatically, stock price alerts, the ability to send messages to friends even if they're not online when you are, a Quick Compact mode that hides the Messenger tools to maximize your viewing area, Messenger Themes, the Online Presence, a small HTML "button" you can put onto your Web site to allow your Yahoo buddies to instantly see if you are online, and voice chat, which allows you to talk for free to anybody else on the Internet. If you have a microphone and speakers, you can talk to other people on Yahoo with no long-distance charges. Using a Webcam, you can see who you are chatting with, or view the Webcam of any Yahoo member who has granted you access.
Version 5.0 introduces IMVironments, custom themes that you can add as backgrounds to your messaging window. This version also features a fix for a vulnerability that could allow a hacker to impose a "buffer overflow" attack, which could delete files or cripple a computer's security.