Either a problem with the browser or the connection. Do you have another browser you can use temporarily? If not then the only way to install one would be to open Internet Explorer, so you'd have to try testing the connection in various ways.
Best starting point is first to restart your computer, and if that doesn't work, find your router and turn that off and back on again. If that still doesn't work then I'm out of ideas for now and more information might be needed (eg what version of Internet Explorer, what computer you have, who provides your internet and so on).