I cannot open the CS6 Design Standard file from the downloads page.

use a different (wired) connection and/or a different browser and/or a download manager.

and/or you could try a different server:

if you follow all 7 steps you can directly download a trial here:   Download Adobe CS6 Trials: Direct Links (no Assistant or Manager) | ProDesignTools

and activate with your serial number.

if you have a problem starting the download, you didn't follow all 7 steps, or your browser does not accept cookies.

the most common problem is caused by failing to meticulously follow steps 1,2 and/or 3 (which adds a cookie to your system enabling you to download the correct version from adobe.com).

failure to obtain that cookie results in an error page being displayed after clicking a link on prodesigntools.com or initiates the download of an incorrect (eg, current) version.