To use sites which contain Flash files, use Puffin Browser. 

You can watch videos, play games, and tap into an endless sea of Flash content because Puffin runs  Flash in the cloud. If you are having trouble running a site in Safari or if you see a message to tell you the Flash plugin is missing, try the same site in the Puffin Browser.

If you have opened the site in Safari you can easily transfer it to Puffin without having to search again for it in Puffin. See how here.