Designing and programming in Flash was part of my skillset for a decade, having cut my teeth with Flash in 1999. Over the years, I've seen and done many projects, some of which utilized Flash in very useful ways, while others had no business using it. Sometimes, a Flash implementation detracted from the site's purpose and had poor results (all the while costing them more to build the site in the frst place). Nowadays, companies have begun moving away from Flash but as reminder to website builders everywhere, here is a brief list of places that Flash does not belong (with very few exceptions):
1. Website Intros
Let's get the obvious out of the way. I see almost no use ever for a Flash intro (or really, any website intro), unless your website strategy includes annoying visitors and wasting other people's time.
2. Sites with SEO Objectives
Although it's possible to get semi-decent SEO rankings in certain situations for a Flash site, you're just not going to achieve the kind of SEO success for a Flash site that you can for an HTML equivalent. Granted, SEO isn't an easy game to play even if you don't use Flash (see our SEO tutorial), but if your website strategy has any SEO expectations, stay away from it.
3. Menus/Navigation on an HTML Site
Menus have a singular and key function on every website -- to get visitors quickly to the content they want. The words "pretty," "cool," or "smooth" should not be in the same league as "accessible" when it comes to navigation. A Flash menu runs the risk of leaving many users stranded (not everyone has Flash, including the large user base that surfs with mobile devices). Furthermore, search engines won't get around too well on a website that lacks true links for its menus.
4. Informational/Content Sites
A couple years ago, I did a website for a large church organization that had dozens of menu items and many pages of content per menu item. They insisted on a Flash site where you never had to use the browser scroll, and at the same time, it should look just like an HTML site (which of course, begs the question, "Why are we using Flash?"). Needless to say, they ended up with a very cumbersome website that costs much more than an HTML site, both to build and maintain. Furthermore, visitors complained about the site usability, preferring even a simple text-only site where they could actually get the information they wanted. In general, you'd be surprised how often a visitor will take information accessibility over a great-looking Flash one. If your website's primary purpose is delivering informational content, avoid Flash.
Anyone who has followed the development of the Flash platform will concede that it has come a long way in terms of functionality and programmatic flexibility. With the advent of Flex, Flash is more equipped for application-type usage than ever before. However, I think Flash for e-commerce should still be avoided for two primary reasons:
a) Flash stores can still be pretty complex. Your typical HTML e-commerce site is straight-forward with a catalogue, account, and checkout system, all of which can be edited and modified independently with relative ease. Although a Flash store will have the same basic components, you're still dealing with a platform with more integrative complexity and less room for error. In the last few months, I've come across two websites that have attempted to implement a Flash e-commerce solution. On both, I managed to somehow find a weird functionality bug, and having lost confidence in the site, went elsewhere for my purchase.
b) E-commerce conventions are very powerful. For the last decade, online shoppers have become accustomed to how e-commerce sites work. Any great derivation from what they're used to will often result in lower ROI. Although some Flash carts look really snazzy and may have more functionality than their HTML counterparts, the proof is always in the customer conversion rate. And having worked on and seen sites that have attempted both types of carts, even "ugly" HTML e-commerce sites will outperform Flash carts. Online consumers are used to clicking on items, not dragging items to a "cart section." They want to click "Add to Cart" and "Checkout" and go from page to page. Sure, this may change in the coming years, and yes, innovation is a good thing, but e-commerce conventions still hold too strong.
6. Sites Requiring Heavy Management
Although Flash has a few solid options for content management, if you or your client will be constantly editing a website, Flash can easily become more of a hurdle in keeping it updated. This is mainly because clients always end up wanting to edit more than you tell them is possible. And there are few things worse in a freelancing business than maintaining parts a Flash site for years. If you know a client has high maintenance needs, make sure you address such future issues before even starting the site.
Of course, there are some websites where Flash can be a good choice or at least a "possible" choice. Some such sites include portfolios, promotional sites (movies, product "exploration" sites, etc.), sites with videos or games, and small boutique sites for creative agencies or possibly high-end design products (and even then, it's never a bad idea to have either an intermediary HTML portion or a full-fledged HTML version). Just don't ever forget that every website has a primary purpose, and if Flash doesn't contribute to that, it's probably a detriment and a liability.