If you mean you want your website to connect to the scanner connected to some visiting user's computer then I would say you are out of luck. Aside from the gaping security problem that would occur if a website could read someone's scanner, there are a million other problems
what if user doesn't have a scanner?
how do you write one scanner driver that works on every possible combination of computer and scanner?
* users don't want you to do this. browsers don't want you to do this. scanner makers don't want you to do this.
etc.
Now if you want to scan some document and put it on your website, that's a different thing entirely, but I would expect that you should probably just scan all the documents you intend to host first and just upload them to your server.