On my website at http://www.eyeonthetigers.co.uk whenever I add something new to the sidebar (for example, I’m currently trying to add a plugin which will show the most recent forum posts, but it’d be the same for a simple text widget), the text is bigger and not in the same format (links are underlined, and it gets put in large italics) as the text currently in the sidebar for Categories, Pages and Archives.
What do I need to add to the CSS so that a list will appear in a new widget in the same format as what’s currently in the sidebar?
Usually, you don’t need to add anything to the CSS.
However, you will have to keep in mind that almost every sidebar is a huge nested lists… so the text inside text widgets often has to be inside li or ul and li tags.
Try to validate your site after adding a text widget and it will tell your where do you miss the proper tags.