Why do I have to change my web browser to view You Tube videos?

Recently I was told by my brother that You Tube will be changing something regarding which types of web browsers can play their videos. Presently I can view them using either of my 2 web browsers. I have a Mac OS X version 10.3.9 desktop computer. Presently using Firefox version 2.0.0.20 for my primary web browser and Safari version 1.3.2 as my back up browser. My questions are (1) has anyone else heard about this change on You Tube regarding not being able to view their videos if your web browser is not the right version to view them and (2) if this is true...will the browsers I have work or will I have to upgrade them and if so how do I go about doing that or finding a new browser that will work with my Mac? Thank you for your replies.Why do I have to change my web browser to view You Tube videos?
I have heard nothing about that, and I'm pretty sure if that does happen you can always change your browser then.

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