Not neccessarily difficult. It could be done for local files at least.
I'm not sure about using the FTP commands for downloading webpages, since it works differently to HTTP (the way Firefox, Internet Explorer, etc access web pages).
If you wanted to use FTP, you would need a user name and password for the site you want to connect to. Having a FTP user name and password for every web site would be impossible.
However, if it was you own FTP site you wanted to connect to, you could:
1) Log on to your FTP site
2) Download the html file, disconnect from the site.
3) Open the html file for reading, move through the file and extract the tags (put them in an arrays)
4) Iterate through the arrays and render using DBC "objects" (sprites, text, etc). If you wanted a scrollable page then each object would need to be rendered with a vertical offset from the "top" of the page.
This should work OK for basic web pages and would be an interesting DBC learning exercise (I'm half tempted to attempt it myself - but I'm busy lol). If you wanted the program to load pages that were online then you would probabaly have to make use of a DLL file.
However, if you simply want to take the user to your website using their default web browser then go the route that Robert The Robert suggests. Here's some code:
website$ = "http://www.thegamecreators.com"
print "Visiting ";website$
execute file website$,"","",0