There are so many new and exciting features of Ajax, Dynamic HTML, and other "bleeding edge" technologies, but it can be hard to decide whether to use them. Before you decide to write your pages at the edge of HTML, there are some things to think about:
1. How many new features are on the page already?
If a page has too many flashing lights, gizmos, and special effects, your readers may be turned off rather than impressed. Also, things like java applets can take up system memory for your readers and can cause their browser to crash if there is too much going on.
A good rule of thumb is to limit your page to 1 special effect of any kind. This includes music, streaming video, java applets, Ajax applications, and Dynamic HTML.
2. What are you trying to achieve with the effect?
Try to design your pages with purpose. If you want a rollover, add it to the areas of the page that might not be clicked on if you didn't call attention to them. Use dynamic positioning to serve a purpose.
Fancy effects that have a purpose will enhance your Web page rather than detract from them.
3. Can you achieve the same effect with an older technology?
The older your effects are, the more likely it is that they will be supported by multiple browsers. If you can create a motion effect with an animated GIF, more people will see the animation than if you use DHTML, Ajax, or Flash.
The more you can keep your site browser non-specific, the more readers you will have.
4. If you want a browser specific effect, have you thought how other browsers will see the page?
Even if you want your customers to view your site with Internet Explorer, you're certain to get Firefox, Opera, and Safari viewers. But if you show them nothing, you'll lose readers you could have saved with just a few more lines of HTML.
When using an effect, keep in mind how other browsers will see (or not see) the effect. Many effects have built in support for non-compliant browsers. For example, if you use the <iframe> tag, you can include text inside the tags that can explain what the non-iframe compatible browser is missing.