Allow user controls
Cardean University offers a good example of user control within a Macromedia Flash animation. The site makes it so that the user can pause and resume the animation at any point.
Let the user have control over as much of the Macromedia Flash content as possible. The user should be able to stop animations at any point, rewind them and toggle sound with a click of the mouse. The Macromedia Flash contextual Menu (the menu the user gets when right-clicking or control-clicking a SWF file) is a good starting place for this practice. It allows the user to zoom in on hard-to-read text, rewind without reloading and adjust the quality to reflect their processor power. That type of control should never be disabled.
Allow a "skip intro" or avoid them all together
Intro animations serve to tell stories and inform the user while the rest of the Macromedia Flash content loads. Intro animations can be preferable while Macromedia Flash content loads over a slow connection. Still, intro animations will drive users away from the site if they feel that the information they are receiving is not directly related to their goals.
Intro animations should not be used as content in of itself unless the user is provided the opportunity to skip it. Have the '145;skip intro' as part of the HTML and not part of the intro animation. This will allow the user to skip the intro immediately without having to wait for the download in order to bypass it.
Avoid using intro animations that impede users from accessing the homepage of a site. Oftentimes the same content that is in an intro movie could easily be embedded in a traditional HTML homepage and stream in the animation after the rest of the page has loaded.
Information on setting, reading and using cookies within Macromedia Flash can be found in the article "Bake Cookies for your Visitors with Flash".
Run intro only once
Set a cookie at the end of an intro animation to indicate that the user has already seen the intro. Next time the user comes back, have the site search for that cookie value and redirect them to the next page of the site. On the destination page make a link to provide the user the opportunity to play the intro animation if they so choose.
Set a cookie value based on the speed of a user's connection. Setting the cookie can be part of the pre-loader. Developers can use ActionScript to track how long it took to load a specific amount of data and set the cookie value accordingly. Visitors who need a long load time (under 20k per second) have a low-bandwidth connection and need content geared for low bandwidth delivery. Visitors with a short load time (over 20k per second) are high-bandwidth users and have the capacity for all the bells and whistles.
Detect the version of the Macromedia Flash plug-in that a user has and write a cookie that has the same value. Users with the latest plug-in will be able to take advantage of the XML support in Macromedia Flash 5. Users with version 4 of the plug-in can access the Macromedia Flash printing in that program. By determining the Macromedia Flash plug-in version the user is using, the Macromedia Flash content can deliver the most suitable content to them.
Color Blindness affects seven percent of men and four percent of women. This means that they cannot distinguish red from green, or that they see red and green differently from most people. When designing Macromedia Flash content with reds and greens, you may want to offer the user the options to switch the colors to blues and yellows: colors that are not impacted by color blindness.