I suggest you to download Google Chrome and use it instead of Opera or IE or Mozilla, some browser still gives unknown problem often. I suggest you to either use Chrome or Mozilla than other browsers.
Additional tips to remove issue of 400 Bad request Your browser sent an invalid request - as follow;
Clear the Cache from your system
Remove the Cookies and Try browsing again
If you are using Internet Explorer and getting this message then follow the steps given here.
Go to IE's setting
Tools -> Internet options -> Advanced Uncheck it, show friendly HTTP error messages. Now you can get a more detailed message with reason.