I don't use Flash as iPhones don't allow it (unless you developed in Adobe Flash Media Server 4.5, or have installed it the hacked way), and Adobe announced last year they are giving up on Flash content for mobile devices late last year.
That not withstanding, if your point is to just get Safari to preview, then first try the suggestions on this post:
https://discussions.apple.com/thread/4014920?start=0&tstart=0
You can also try uninstalling and reinstalling Safari, which may or may not help (not advised unless you have to though).
Another - LONG - method is to use Boot Camp, VirtualBox, or VMWare, and install Windows on your Mac. Then download Safari for Windows, and check it that way.
You can also use Chrome to preview (which uses the Webkit engine like Safari does). Here is a list of browsers that all use Webkit:
http://trac.webkit.org/wiki/Applications%20using%20WebKit
Another list:
http://en.wikipedia.org/wiki/List_of_web_browsers#Webkit-_and_Trident-based
