yeah flash and javascript are fine as long as the website isn't targeted for mobiles because there are some mobiles that don't support flash in that case you ought to think to move on to javascript entirely. moreover flash is a bit heavy so it takes a bit more time to load the website on the other hand javascript is light and support for any browser from mobile to desktop but it takes a lot of time to develop an interactive site unless use JQuery. also flash isn't SEO friendly which means whatever you put on flash ain't indexed by the bots of search engines but now there are some sites that also collect flash contents though it's not reliable. so I suggest you to avoid flash and entirely focus on javascript since it supports for any platform. additionally now there is a trend that some developers tend to use WebGL,Canvas Tool implemented in HTML 5 and supported by most of latest browsers it's a bit convenient approach if the website is targeted for desktop environment but the disadvantage is if the client doesn't have a latest version of the browser the implemented features can't be seen.