browser to target for?

[CareBear]

I have Internet Explorer 5.0, 5.5 and 6.0 installed so I'm not too concerned with testing on those.
I'm open to suggestions for other browsers though :)

For Netscape I'm thinking of installing a v4.7 copy but for more recent ones I really don't have a clue. Which one is still used by a fair amount of people: v5, v6 or just go with the lastest v7?

Is there a significant difference between Netscape v7 and Mozilla as far as handling of CSS and Javascript goes?

Is Opera worth testing against and if so which version would be best?

[manni]

Old Netscape (4.x) may be good for testing (it's not necessary to have exact same layout with it, main thing is to get page usable for NS 4 users). Mozilla and new Netscape renders site the same way (Netscape is based on Mozilla). Opera (6 or 7) is also good to have. If your code is 100% valid (http://validator.w3.org/) there should be no problems with new browsers (IE 4 ->, Mozilla 1.x and Opera 4-5 ->).