Yahoo! Messenger for the Web (beta) has just launched and includes an exciting new feature: Message History. The feature, which is available in select versions of the product, saves IM conversations in your account on our Yahoo! servers.
gtalk also provide this feature for their users .You can now access and search your message history from any computer -- just like email. Whether or not you use this feature, your IM friends and others you communicate with on Yahoo! Messenger may save conversations in their Yahoo! accounts.
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yahoo messengerLabels: save yahoo chat history, yahoo messenger tips