Custom Error Pages
This section enables you to create more user friendly error pages (for example with your site logo and a link to your homepage) than the standard versions for the following errors:
400 - Bad Request
Clicking on each link lets you edit the contents of each file directly and insert custom tags to display more information about the error.
Alternatively you can design these pages offline and upload them via FTP like normal pages to your public_html folder. Remember, these files must have the .shtml extension.