We will first of all look at the visuals of each browser.
Internet Explorer
Mozilla Firefox
Opera
As you can see above, all the browses have similar characteristics: a menu at the top, address bar and the page displayed. You will also have navigation buttons etc.
A small point to make about Firefox and Opera; you will notice that there is a search field at the top right that allows you to use search engines without passing to their web page. You should know that this search field is completely customizable under Firefox and that it is possible to use a large number of search engines (Wikipedia, Google, Amazon, eBay…).
Visually speaking, there is not a lot different between them all. Internet Explorer and Firefox are designed very similar. Firefox has a row for its tabs, but as the buttons don’t take up two rows, the space taken up is about he same. I personally prefer the design of Opera. It is rounder and more up to date, looking less like an application from Windows 95. But this is just a question of taste.