help, please....

[daddymcbeal]

hi, i have created a really basic site (well its just a welcome page really, i will complete the site of the next few months)
i have bought my domain name and pointed the dns records to the ip of the webhost server. (i think i have done this right)
when i browse to w w w.domain.com i get an error page
when i browse to h t t p://doman.com i get a list of the files that i have published to the site, i can see my default.html page/file and when i click it i see the page that i want to display.

1 - why does it not just show the site when i go to w w w.domain.com ?
2 - why does it show me the file list when i go to h t t p://domain.com ?
can anyone tell me what i've done wrong????

any help would be great
thanks
ian