Everyone has a website these days, but how effectively are they executed? Do they look the same on different computers? More importantly, will they stand the test of your users?
No matter how you design your site, people will try to use it differently. If you try to build it specifically to work in Internet Explorer, people will still visit with Firefox and Safari. Placing an annoying "Best used in..." message at the top of your site is just that - annoying. You can't dictate how your customers browse the web any more than you can tell them to buy your brand rather than your competitor's.
If it were that easy, we'd all be out of jobs.
Smart web design takes this into account and still delivers visually compelling sites. First of all, smart designers will avoid the use of third-party applications (read: Flash) as much as possible. Yes, they look nifty on your screen ... but try viewing your site on an iPhone. See what I mean?
Flash is not supported by the majority of mobile devices, including the iPhone. To build your site in Flash or to have heavy Flash elements on the page is to ignore your most tech-savvy and connected customers. In addition, many people don't always keep their computers up-to-date. Unless they're on top of things, a home computer might not have the latest version of the Flash plug-in. To tell someone they have to go to another site, download and install software, and then come back to view things is, frankly, rude.
Imagine what would happen if a night club turned people away at the door because their ties were dated. How well do you think business would perform in that environment?