A plug-in is software that acts or interacts with another piece of software. Shareware is a term for freely distributed software for which you are expected to pay a small fee. The fee is usually just enough to cover the cost of distribution and encourage further development of the product. Contrast this with freeware which is freely distributed and free to use software. A smiley , though you won't see many on the Web, is something every e-mail user needs to know about.
Smileys help to convey emotion where written words fall short.
Most e-mail systems don't accommodate images so a smiley like this can't be used. URL refers to the Uniform Resource Locator. White space is the space on your page that's not covered by text or graphics. Layout and design experts say that your pages need some white space but not too much. That's up to you.