I haven't however blogged about the solution for this.
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#1: Personally, I went the route of getting newest available Firefox for 10.3.9. Looks like Firefox 2.0.0.x works for OS X 10.2 and newer. Oddly enough, I couldn't find a download link on Mozilla's own pages, so let's grab it from OldApps.com. Now, Adobe's regular pages work!
However, you might not happy with that, no sirs. (But, why aren't you? Firefox 2 is the best browser you can get on that old OS and machine you have there. Safari 1.3 is ancient. FF2 may not be the newest,but it's the best you can get with Mac OS X 10.3 so don't be like that.)
#2: Alternative solution is clicking on this link, where I already clicked on "Agree and Download" for you. Even closer, here's a direct link to the DMG file. To install, double click on DMG file. An icon appears on your desktop; open it. Then drag the icons on the left into folders on the right (the background of the window is very suggestive of what you have to do).
Now go and watch flash-video movies on that iMac G3 you have there (which is precisely why you're stuck with 10.3.9, right? At least I am)
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In case these links don't work a few years after 2009, post in comments and I'll try to get this for you. I might not be able to help you, but asking won't harm. I won't put alternative link here, since Adobe doesn't like people redistributing their player. They do however like breaking their site for the target audience of the software download they offer. Ugh.