why i cannot download jdk from oracle web site directly without AuthParam?

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http://serverfault.com – that is download with the following command, why it fails to download that file? wget http://download.oracle.com/otn-pub/java/jdk/6u35-b10/jdk-6u35-linux-i586... the following command works, but that AuthParam may not work after a while, why? wget http://download.oracle.com/otn-pub/java/jdk/6u35-b10/jdk-6u35-linux-i586... how this AuthParam option is implemented? why i cannot download without this parameter? and why i can only get this parameter using explorer? is rewrite used in the oracle server when deal with wget request? why (HowTos)