Accessibility, effective visual appeal, and efficiency are a few of the principles we implement into every website that we produce for our clients. With Flash elements, you can create eye-catching web pages that have a “wow” effect, complete with moving pictures and changing words that can draw a visitor deeper into your website. A good looking website does matter, and Flash can help trigger an emotional response in your potential customer that can result in higher online bookings.
BUT, there are several risks we take when incorporating Flash elements into a website. One of these is that users must have a plug-in with their internet browser in order to view the Flash element. If a visitor viewing your site doesn’t have this plug-in installed, they will not see your spectacular display, just a rather dull link to install Adobe Flash player. They may not have the patience to install the plug-in, and may choose to leave your website. It’s a bit ironic, but the same thing that draws some visitors deeper into your website may turn others away.
Another thing to remember is that search engines can't see 'into' Flash objects, therefore none of the content inside a Flash element contributes to your SEO efforts.
Take a look at this BnBwebsites article that explains more about what Flash is, how it can help and/or hurt your website traffic, and how to decide whether or not it's right for your site: To Flash or not to Flash