To get these sort of load times, you will want all web pages to be less than about 50K. A pretty hard task. These things can be measured. But you also need to make sure that your site looks professional. It should have a consistant look and feel, be easy to navigate, and show all relevent information. And then there are the taste issues.
Web browsers are really quite clever things.
But some browsers are more clever than others, so the real answer is to make sure that all of your HTML code is actually correct. In fact, any decent HTML editor will have one built in. So you need to validate for a certain version. Usually it is best to make sure that your code conforms to the lowest HTML version you think you can get away with - probably V3. If you don't, then older browsers may have problems with your site.