Forms

[Servoc]

Is there anyway of coding a submission form so that it would provide the default email address of the user completing the form without them providing their email address?

What I am looking for is a way to see if someone in particular is going to one of my sites. I was thinking that I could use the form to create an entrance button to my site and then they wouldn't even know they were submitting a form.

I'm using Homestead as the host for the site.

[Twey]

The short answer is: no.
The long answer is: no, because this isn't information that's given out by the browser. You can usually identify someone by either their IP address - which can change, but not very often unless the user is on dialup - or a tracking cookie.

[mwinter]

You can usually identify someone by either their IP address - which can change, but not very often unless the user is on dialup

That isn't necessarily true, and again AOL is an example. In this case, AOL uses load-balancing proxy servers; one request might originate from one server, but a later request could be shifted to another to reduce load on the first.

Also, note that AOL says that requests are usually routed through their proxy system. That means that occasionally, you might get a direct request from an AOL user, and so again there is the chance for you to receive a different IP address.

or a tracking cookie.

Of course, you should make sure that you can cope with rejected cookies. Not everyone allows cookies because they don't want to be tracked.

Mike

[Twey]

In this case, AOL uses load-balancing proxy servers

It's possible to find out the address of a machine behind a proxy (I think - something about X-Forwarded-For? Do some proxy servers not support this?).

Of course, you should make sure that you can cope with rejected cookies.

A combination of the above methods should work.

[mwinter]

It's possible to find out the address of a machine behind a proxy (I think - something about X-Forwarded-For? Do some proxy servers not support this?).

Proxies can include the original address, but they don't have to, it can be disabled, and it's easily spoofed. The OpenInfo site provides some information about the x-header.

Still, there are other considerations, such as NAT. On the whole, you just shouldn't attach a great deal to IP addresses on the Web.

Mike

[Twey]

There you go, then. You can't (reliably). You can try all the above methods, but don't rely upon them too heavily.