Twitter’s new design changes the dimensions required for backgrounds with content. Your customized background, designed to optimize the available space won’t work with the new look. For example, BestBuy’s background is simple and fits the brand well. It includes a list of URL’s so people can find all of their sites. It looks like this with the old version of Twitter:
Changing to the new version reduces the visibility of the URL’s as seen below.
If you aren’t using the new Twitter, take a test drive now to see how your background looks. Don’t worry, you can return to the old version by clicking the down arrow next to your user ID on the top right of the page. It allows you to exit the preview.