With most domain names the www. seems to be optional, so perhaps Google just happens to have found the page without the www. first. I don't think it's important.
When you use the directory name like www.sussexwebdesign.com without index.html the host server sends you to an index file with any extension like .htm .html .php .css usually in that order if you have more than one.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.