When I started teaching JavaScript two years ago, I wanted to make sure the official reference guide was available to my students. At one time, it was possible to download the reference and user guide for the various JavaScript releases from Netscape. Unfortunately Netscape was sold to AOL who eventually decided to turf the developer pages, and the links to these resources.
It took some doing but I was able to track down both the JavaScript 1.5 Reference and the Guide. These can be downloaded from the links below:
(Note: Un-zip the file(s) into a target directory, then find the index.html file and open it in a web browser.)
Tonight I was doing some review in preparation for the next JavaScript class (next week), and came across a NEW developers resource for JavaScript, now hosted at Mozilla. This resource seems to offer everything the original at Netscape did, and more! You can see it at http://developer.mozilla.org/en/docs/JavaScript.