Intro
I know a lot of people who downloaded Netscape 6 after years of awful browser experience with Netscape 4. Most of them don't understand why Netscape 6 is so bloated, why it skipped the layer-tags and lack some other background information. If you're one of them, I'll try to close the gap.
Open-Source
In January 1998, in the middle of their war with Microsoft, Netscape decided to go open-source with their browser using the project name Mozilla. This was a great step for the community. But there were some difficulties. For example it's very difficult to continue development of such a big project. That's why the development took such a long time.
Marketing
Open-sourcing their browser has other implications for Netscape. The Mozilla project isn't willing to include commercial components into their browser. Because of this, Netscape Corp. sometimes bundles a release of Mozilla with some included AOL software such as the AIM.
Netscape 6.0 was one such release. They (Netscape Corp.) grabbed a copy of Mozilla 0.6, added some commercial components, released the whole bunch as Netscape 6.0 and created a big media hype. In my opinion this was the worst they could do for the popularity of Mozilla. As you can read from the release number, Mozilla 0.6 was far from being usable. (Everything below release 1.0 is in the testing phase)
So in fact Netscape released a test version and declared it stable, usable and so on. No wonder the customers lost their trust in Netscape! But if you're still interested, I recommend you to jump over to the Mozilla site and grab a fresh release. The project evolved a lot since release 0.6 and I can now recommend it.
Non-proprietary
Let's now switch to a totally different topic: One of the main targets of the Mozilla project is to fully stick on the standards. For example no proprietary HTML tags as <layer>, <blink> or <marquee> are included. Because of this Mozilla isn't backward compatible to Netscape 4.
For example DHTML scripts written for Netscape 4 need to be rewritten for the Mozilla browser because Mozilla implements the W3C DOM instead of the Netscape layer model.
This is a bad thing for the maintainers of existing Web sites but it's great for the development of new scripts! In the future you won't need to develop the same script for every browser. One script will suffice. You can even start with this just right now. A script written for Mozilla should work with Internet Explorer 5, too. If you can live without the 4.x browsers, this is the way to go. Read the DOM specification to get started.
But why did they do this? I guess that this has to do with the project goal set by Netscape. They want to create a good alternative to Microsoft Internet Explorer to prevent them from extending their browser monopoly. One of the worst things Microsoft does is adding proprietary features to their browser. So the Mozilla project needs to distance itself from Internet Explorer.
Summary
I hope I could explain you some of the negative points about the Mozilla project. Don't hesitate to contact me, if I forgot something important or if you have any other feedback.