Share 'Marking your Twitter feed (or any imported feed)'

I import my Twitter feed into my tumblr at topherchris.com, but it's always bugged me a little that my "tweets" look like regular posts. I want them to look different, to be marked in some way so readers can easily discern if they're reading a Twitter post or a blog entry. For more on feed importing: The Feeds page in your tumblr dashboard opens up an infinite number of possibilities -- from imp…