Twitter has begun offering an embeddable button for one-click subscription to a Twitter account associated with any website, called the Follow Button. Previously, a website owner could link to their Twitter profile page off-site but users had to visit that Twitter page and click to follow the account from there.
Users interested in subscribing to updates from a website itself can, as always, subscribe to the Really Simple Syndication (RSS) feeds offered by many sites for years. Those are the orange buttons with the little white lines on them, and without the word Subscribe. RSS requires the use of a different application, called an RSS reader, where a user is probably less likely to encounter poorly written little jokes or the daily ennui of Hollywood starlets. Or your mom, who is more likely to Tweet than knowingly publish an RSS feed.
As Twitter power user Kevin Marks said today, it would be nice if the button included rel=”me” in the code. That way outside parties analyzing the social graph across the web will know, programmatically, that the two pages are owned by the same people. Twitter profile pages have links in the user bios that include rel=”me” markup already.