Even if the Netscape Navigator 2.0 isn't in beta any longer JavaScript is still being developed. We will see many changes in the future because this scripting language is still very young. But at the moment we can already work with many features seriously. Some things of JavaScript are still about to change. The best example is the one I had trouble with myself. I had the property lastmodified in my document. This was correct for Netscape 2.0 beta2. But with newer versions this property changed to lastModified. You might think this is just a small mistake and the browser does not bother. But for the browser lastmodified and lastModified is something different. JavaScript is case sensitive! So you have to be certain about the case!
Some functions that are mentioned in the documentation provided by Netscape are not yet implemented. Still there are some nasty bugs. Some only affect some users. For example there is a known problem for Mac users. The date- functions do not work properly. Please have a look at the FAQ (frequently asked questions).

I hope you understand that I cannot know what further changes are made to JavaScript and in how far this is going to affect your scripts. But as things are moving so fast today I don't want to wait until the final version (if things like this exist today...) is ready. And I have the feeling you don't want to wait either... And if you realize a problem with my examples please write. I will write further parts for this introduction. So be sure to check back once in a while.