Just open the folder up normally so you see all the files then right-click somewhere in the blank area and you'll see "customize this folder" and go from there. You can design your own HTML and include whatever references to servers local or remote.
Nevermind, that's for desktop.ini settings. For webservers you'll probably want to make a default file such as index.htm or default.htm and stick it in the directory. If this folder is totally protected by .httaccess then this won't work and you'll have to edit .httaccess with a text editor or remove it depending on your needs.
If your site is displaying "popup windows" it's probably one of those free hosting sites like angelfire or tripod. I dread that kind of coding and you should probably consider a paid hosting site or free one that doesn't do popups.