Interactivity
Flash’s many great features, specially the ActionScript has opened up enormous possibilities for programmers and designers. They can build web-page with interactive features for example flash-based games, feedback forms, photo slide show, charts and much more. This sort of attractive interfaces that web surfers will see on the web will always make them come back to the same site again.
Consistency
Flash-based websites gives you freedom from cross-browser compatibility problems. With Flash, no more worries about how a particular CSS code displays differently in different web browsers. A good thing about Flash is that when we set our site layout in Flash, it will always appear the same in Internet Explorer, Firefox, Chrome and other popular browsers. As long as the user as Flash Player installed, he will be able to view the Flash-made content with no problem.
User-friendliness
With Flash, it is possible to express something to a site visitor in a much more efficient and better way. Flash-based sites are attention-getting and eye-catching. The site visitors enjoy more on the site, understand any message conveyed better and they are more likely to spend more time on the site and visit it frequently .
File size
Flash-built graphics and animations are light weight. Hence it will take less time compared to standard images and animation to upload the Flash content to the web server.
Loading time
Flash content takes longer than usual to load compared to regular images and text. This might cause some visitors to loose their patience and exit the browser or hit the browser’s back button. The heavier your Flash content is, the longer it will take to load and the more you risk losing visitors.
The Flash player
Flash requires users to have Flash player installed on thier computer to view Flash movies. It is likely that not everyone has it installed on thier system and when the site will tell the user to install it, not everyone will be willing to download it only to view your site. This will result in decreased users to your site just because you used Flash-made content.
Website Traffic
A website having Flash content in it would not be indexed by most search engines. This means your website won’t be able to rank good in search engines. Consequently, there will be less traffic coming to your site.