It's been a week full of announcements from Twitter: first the social network debuted a new (arguably Facebook-like) profile design, and today it's officially introducing real-time notifications on the web. We first saw the pop-up alerts in late January, but it appeared to be an experiment visible to just a handful of users. Now -- or, more accurately, "over the coming weeks" -- any time you're logged into Twitter.com, you'll see a notification window alerting you to any replies, retweets or other activities.

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