When you login to wordpress, you see the default wordpress logo and if you click on this, it takes you to the wordpress.org website. This tutorial will teach you how to change the image, and the URL.
I recently had the problem where the latest tweet was not being displayed on our site. After a while searching I found the cause. Apparently Twitter no longer supports the original url which is used in the code of the theme. To fix it
Here is a quick tutorial for adding an anchor link to a WordPress page or blog.