web server dlink 624s help please

Recently purchased dlink di 624s router
has a web server function on it.
Also has two usb inputs which can be used as a print server and usb HDD
It says in the manual to put a web page on a usb key and select this in the web server options which I have done.
Now i am stuck not sure how to access web page / server?
Manual is useless for a novice?
I was hoping too set it up to allow my folks in the uk access to look at pics ect.anytime without my pc being on just the 624s.
THere is a lot of talk about port forwarding ect on the posts.
I understand this and have these set up for odd things but i dont understand if the server is on the 624 with the files on the usb disk there is no [point having the ports open on my pc? is there?
I am confused all round I think
Help would be appreciated in any form
Thanks