I think this image, seen in the sidebar of the main site, violates Twitter brand guidelines in that the site's logo is superimposed on Twitter's logo.
Do: Use our official, unmodified Twitter bird to represent our brand.
Make sure the bird faces right.
Allow for at least 150% buffer space around the bird.
Use speech bubbles or words around the bird.
Rotate or change the direction of the bird.
Animate the bird.
Duplicate the bird.
Change the color of the bird.
Use any other marks or logos to represent our brand.
Promoting your Twitter account
Use one of the Twitter buttons as a link to your account online.
Use one of the Twitter bird logos with your @username nearby in print.
Type Follow us on Twitter followed by your @username when you’re unable to show the Twitter bird.
Manipulate the Twitter bird.
Use any other artwork from our site, such as the verified badge.
Create your own buttons or images using our logos unless technically necessary, such as in signature bars. If you do, use this resized version of the Twitter bird.