How to add URL?

[toplisek]

I have Website Thumb Generator and testing.

How to add URL and path as my website shows me an error like:
Site URL must be specified.

I have added path like:
$thumbnails_folder = 'public_html/.../images/';

1. How to add correct path?
2. How to add variable URL as  there is error message like: Site URL must be specified.

[toplisek]

I have solved error regarding URL as it does not show me anymore error like:
Site URL must be specified.
I have added Get function like:
error_reporting(0);
if(isset($_GET['http://www.microsoft.com '])){
$website_url = 'http://www.microsoft.com';
}

Now it shows me an error:
Thumbnail Generation Error. Thumbnail not created.

How to do correct path as I have $thumbnails_folder = 'public_html/.../images/';