“If you build it, they will come” might be the line from Field of Dreams but the same theory doesn’t apply to websites. What’s the good of building a great-looking web site that no one knows about, or can find? Unfortunately, that is the reality of building websites entirely in Flash.
It’s not just websites that are built entirely in Flash that have a problem. Many websites contain an enormous amount of content that can only be seen with the human eye. Think about all the PDF, sound and other rich media files out there. Can this content be indexed by search engines? The answer is yes and no.
Why should you care about search engines? Since the launch of Yahoo (merely a directory of sites) many years ago, and the very first search engines (WebCrawler, Infoseek, Altavista and many more), people have used them to hunt down specific websites by searching for relevant content. If your content isn’t optimized for search engines, then it is almost impossible for people to find your site. And without this traffic, all your work in building that site is wasted.
Alan Knecht specifically discusses the issues surrounding Flash, PDF content, audio, and other rich media files.