The concept is simple, and benefits are tremendous. Create an "engine" with basic functionality and allow for expansion by third-parties in a standard and organized way. Thus, for example, even though Adobe Photoshop performs an incredibly number of functions all on it's own, authors felt it was necessary to allow others to contribute their skills. They did this by providing plug-ins and filters.

This also, not entirely coincidentally, got around concept of "open source" which has been debated all over internet for years. Pure open source is code which can be downloaded and modified by anyone - Unix is a good example of this. At other extreme is virtually all of Microsoft's products - sources are not made available to anyone except under specific and [legally] controlled circumstances. Plug-ins get around this argument by allowing product to be expanded and it's behavior changed without releasing source code to general public.

The concept of plug-ins actually came into reality back in 1995. The Netscape browser developers had a problem - there were few, if any, accepted graphics and multimedia (videos, sound and such) standards available on web, yet browser had to be capable of displaying graphics and multimedia. The developers did not want to restrict their browser to just a few standards (which may or may not have become accepted) and they certainly did not want to release a new browser every time a new multimedia format was created.

Thus plug-ins were born. This solved problem very well. There was now no need to restrict formats or modify and distribute a new browser. All that needed to be done was create a plug in which handled format. And best of all (for Netscape) this plug-in was generally created by some other company.

There were problems with plug-in concept, however.

- Back in days of slow modems, it could take a very long time to download a plug-in

- Plug-ins could crash operating system or cause it to become unstable.

- If a visitor chose not to install a plug-in, then multimedia object would not display.

- Malicious designers could conceivably introduce security risks through use of plug-ins.

Soon afterwards Microsoft got on bandwagon with it's own version of plug-ins for Internet Explorer. They called their version ActiveX and made them a little more automatic (by adding some custom code to operating system). Ask anyone at Microsoft (especially at training classes) and you be told that future is ActiveX. However, these controls have exactly same problem as plug-ins with a terrible security model to boot (any security model which requires an end-user to make a decision as to whether or not unknown code is trustworthy is certain to fail).

Of course, most coveted data is an email address. This is because email address allows visitor to be contacted over and over again in future. This, in turn, improves odds that something might actually be purchased (assuming site has something for sale) or that message is read and understood.

In order for a webmaster and company to be completely ethical, uses of this information need to be clearly spelled out in simple, plain English. This is called a Privacy policy, and all well designed web sites which ask for any kind of personal data should include one. This is not a legal requirement, it is simply common courtesy. You are asking for something, and you should disclose how that is going to be used and protected (if necessary). This allows people to make informed decisions about what they want to tell you.

What should a privacy policy include? Some of my suggestions include following.

Email usage - If you are asking for an email address, then you need to tell your visitors exactly what you plan on doing with it. For example, on our web site we ask for an email address for guestbooks, feedback and joining a mailing list. In first two instances, we do not use email address for anything except a thank you and never send anything else, so this is stated in privacy policy. Of course, we do send repeat emails if a mailing list is joined, but we don't give those email addresses to anyone. This is also clearly stated.

Cookie usage - If your site uses cookies, you should explain completely and fully what they are used for an how long they persist (remain before they are deleted). The press has made a big deal about cookies, and because of that people tend to have very negative opinions. This makes it very important to explain exactly why you are using them.