Dropbox is not a commercial web host. It's more like a file storage space. I've never tried using it for hosting a web site but I guess you could for limited use like sharing the link with your friends or co-workers until such time as you want to get a real web site going.
If you want to run any server-side scripts, Dropbox can't do that. You will eventually need to procure web server space from a commercial web hosting company.