If you are unable to download TweetDeck from www.tweetdeck.com due to Adobe Air errors, or the "Download Now" button not being visible, you should try the following:

• Ensure you have downloaded the latest version of Adobe AIR from http://get.adobe.com/air
• Download the latest Tweetdeck AIR file from http://tweetdeck.com/go/download/tweetdeck.
  IMPORTANT: Do NOT click "Open with...", click Save File and save the .air file to your hard drive
• Locate the TweetDeck_x_xx.x.air file (filename depends on the version) on your hard drive and run it.
• If you have Adobe AIR installed correctly, this should launch the installation routine
• Follow he prompts as normal to install TweetDeck

If you have any errors or other problems (eg "Error #0", "Damaged AIR file") installing TweetDeck, please check out this FAQ. 

Also see this article from Adobe regarding troubleshooting Adobe AIR installation issues.

If you are still unable to install, feel free to log a request with us by clicking "Submit a support ticket" from the top menu bar of this site.