By now you have probably heard that you should not use flash on your website, as it is bad. But do you know Why Flash is Evil? Using flash element on your website will probably make it look good, and also enable you to do cool stuff with your design. The bad thing about it is that it also make your website load slower, and your flash content is no readable by search engines. These two will have a negative impact on your search rankings, as faster load time means higher ranking, and more content means higher ranking. To point out how bad flash really are for your website an organization was created, it is the Flash Sucks Organization. There are many reasons not to use flash, here I have listed a few of them.
Whereas the ground rules of marketing emphasize the concentration on the users' needs, Flash websites ignore them. Take the infamous site intros and splash screens that are as much annoying as the 45 minutes of advertising and previews in cinemas. Or another example: the sound effects - they are can be especially inappropriate and harmful when you are browsing the Net from a cubicle in a quiet office or from home in the late hours.
Despite of the DSL Internet access being available almost everywhere, there are still lots of people surfing the Net via dial-up or other limited bandwidth connection. Flash files, especially those using sound effects, embedded movies or bitmap images, can take a while to load.
Some Flash designers use meta refreshes or other tricks to disable browser's Back button. As the famous usability expert Jacob Nielsen says, The Back button is the second most important navigation element after hyperlinks. People not able to use Back button will click the third most important navigation element - that X button in the top right. Besides, if you are going to promote a Flash site via PPC, you should know that Google AdWords doesn't approve pages with disabled back button.
Building Flash-powered websites is wrong. Storing your content in Flash movies is wrong. Implementing site navigation in Flash is wrong. Then why are there so many Flash sites? They look pretty with all those neat vector graphics, gradients, animations and cool sound effects. Flash is the favorite toy of big designer studios and numerous amateur graphic artists alike. Flash is visually attractive, and in general attractive websites are more successful than the ugly ones (notable exception: craigslist.org). But this is not the case of Flash websites. All the benefits of the nice outlook are overridden by the disadvantages in terms of SEO and usability.
And perhaps the most important: not every search engine is able to crawl and index the content of Flash movies. Even those that can often do it with errors. Even though Google has a limited access to Flash within Websites, Flash-Objects themselves are code-wise not that well-structured like HTML-Documents. This is a big issue, as Google can't find the context of Information stored in Flash within the HTML-Code. This is in particular the case of a website fully implemented in Flash as a single file. Search engines just wouldn't be able to direct visitors to the proper page within that file. What is Flash really good for? Banners and ads - it provides far more useful features then the traditional gif animation. Online games are often based upon the to use of Flash technology and also Flash videos are frequently used in video blogs.
Unless you do Flash yourself, you might face some serious troubles with developers. Some of them code their project to prevent them from editing, thus making you to hire them over and over again as you need to do even the smallest modifications. Aaron Wall in his SEOBook (a highly recommended SEO reading) describes a case of a Flash developer who disabled the back button and then asked $4000 from his client to re-enable it, although the problem was caused by his own incompetence.
Functions like going back and forth, copy and pasting and bookmarking won't work within Flash. This shows, that Flash is not only a problem for disabled users, but also in everyday use. The conclusion to all this: Flash is evil!