You should not force your users to have a specific web player version. The 4.x web player will happily play back content created with 3.x, using the channels feature in 4.x. (Linking to an old webpage, particularly one not hosted on the official docs server just muddies the water. The current web player `UnityObject2.js` does a good job of detecting if a user has the web player or not, and automates the install for the user, using either java or .net, or, if the user doesn't have those, provides the download link.)
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