Question about what has happened to website

I manage the website for the company I work for. Our website address is:
www.terraceair.com
I was checking out how the website viewed in Firefox, and it was except for a page viewed different that how it was in Sharepoint Designer 2007. so, i went to view it in internet explorer. It then showed up only as a index of/ in internet explorer. I think checked back in Firefox and it does the same. I have the latest versions of each web browser. I have an index.htm page, like i learned in my website creation class i need to have so it does do the list thing like it is doing now. Can someone please help me fix this.