There are a lot of awesome tools and designs out there. As a web designer you have to ask, "can I implement the most advanced tools and design into my site?" Surprisingly, the answer may be, "NO."
The purpose of great design is to retain viewers and convert them into clients, right? Well, have you ever been to a site that didn't work? or a site that was really wide and made you scroll left and right as well as up and down? Have you ever clicked on a link was broken? or a site that took for ever to load?
What did you do? You left. The same is true of people who may be trying to view your site from an older web browser. Today, this is becoming less and less of an issue. Years ago there were distinct differences between web browsers like MS Internet Explorer and Netscape. There are still differences but most browsers can handle most functions and they display different elements very similarly. This being said, there are still users out there that have antiquated versions of web browsing software.
You have to make a decision. Do you want to program for the lowest common denominator (i.e.all users) or only cator to those up-to-date on their software? Here are the current statistics for internet browsers: http://www.w3schools.com/browsers/browsers_stats.asp
Many web design companies will program for the following browsers to include the greatest number of users without sacrificing too much functionality:
Many professionals are designing exclusively to these standards claiming that they aren't interested in working with people not net savvy. Realistically, if you design your own site make sure it works in Internet Explorer 6.xx and newer and Firefox 1.xx and newer then approximately 90% of your potential users will be able to use/see your site properly.
