On some servers that is running Windows OS, some URLs can get an extra backslash, which in some cases could produce 404 error.
If you are NOT experiencing such problem, you dont need apply this fix
In global.php find: $script_url .= (dirname($PHP_SELF) != "/") ? dirname($PHP_SELF) : "";
Replace it with: $dirname = str_replace("\\", "/", dirname($PHP_SELF));
$script_url .= ($dirname != "/") ? $dirname : "";