You either download it from adobe web-page http://get.adobe.com/flashplayer/
or you use Google Chrome, which has it already build in.

Then might be Nick can help, I assume, he needs to know what web browser you use and which flashplayer version. For the time being, might be Google Chrome can do the job.

Till Nick gets here, try looking at your add ins in the browser, I seem to remember having this problem and closing down one of the add ins helped.(can't remember which one though)

Do other computers other than your own have this issue? It sounds like the same issue as before, but it went away when you tried Chrome, and then Firefox worked again, correct? If it also happens on other computers using the same internet connection, then it would be a network issue probably, but if only your computer, or specifically one of the browsers on your computer, then that's the source of the issue. That'll narrow it down a little at least.

flash on iPad ........ mmmmmmmmm :-)

Apple does not allow flash on iOS devices, including iPhones, iPod Touches, and iPads.

You won't be able to use the website with your iPad. You have to use the app.