IMHO the concept of cross-browser compatability is very dependant upon the project...let me give you an example.
My experience in web site design is MOSTLY with an intranet. It is a small-medium sized (about 500 employees) software development firm.
This means a few things:
1)Limited audience--500 people
2)All of the employees are computer literate, most are very fluent.
3)Everybody in the company is running Win98 or NT or 2k, with most running NT or 2k.
4)I have virtually complete control over their browsers. (One word to our Internal Support staff and everybody's browser is upgraded to whatever I want it to be.)
Conclusion:
I make my site however I want...because I know that my audience will be able to see it exactly as I have in mind.
The questions that you have to ask are these:
1) Who is your audience...who do you want your audience to be?
2) At what point does 3% more people NOT matter? (that is, the law of diminishing returns...it is easy to make raise hits on your site from 0% to 3%. It becomes slightly more difficult to go from 3% to 6%...and so on. It is very difficult to go from 96% to 99%...at what point is the extra work NOT worth the extra 3%?)
Once you have those answers...code for that situation.
It is fairly easy to code for cross-browser compatability, at least for most browsers.
If I were doing a 'real' web-site to be seen by the rest of the world, I would code so that it works well in IE4.0+ and NN6 with it not breaking in NN4+. But that is a result of my particular answers to those two questions above...your results may vary.
The problem with IFrames is NOT that they don't work in older browsers...but that they don't work in ANY browser other than IE.
mobrul
[This message has been edited by mobrul (edited 07-23-2001).]