Just out of curiosity.. is there any value or any sequence of characters that when given in the url bar, crashes the browser? im not speaking about any kind of scripts here..
2 Answers
In Firefox, for example, the entire UI is rendered using the same system as webpages, which leads to strange things like:
chrome://browser/content/browser.xul
opening another copy of your url bar, bookmarks bar, so on inside a tab. You can also run JavaScript from your url bar, which can have effects ranging from highly useful to Cornify.
Other than that, modern browsers are really quite secure, and it's getting harder all the time to trick them into breaking.
This isn't exactly current but I believe in Windows 95 typing about:mozilla into IE would cause a BSoD. This was replaced in Windows 98 with an empty page with a blue background. I believe the entire feature was removed in Windows XP