Can't download extension "Page Speed ​​Optimizer [Free]"

I

click on the "GET" button and then redirects to the following page: www.mobilejoomla.com/index.php?option=com_payplans&view=order&task=confirm&order_key=8XRE0BA17447

which is empty and nothing happens

Please wait for a few hours. We were in the process of updating this page when we encountered a minor issue. Everything will be fixed in just a few minutes. I greatly appreciate your understanding in advance.

And how to install it? Does it support Joomla 1.5? Error! Joomla! Setup XML file not found

PageSpeed Optimizer supports Joomla 2.5 and higher.