Hello Vikrant,
Same problem on my end, I am unable to download "Install_Instructions.pdf" from the ESD site. If tried both in the "Master Collection" page and the "Design and Web Prem" page, also for Windows and Macintosh. Maybe all these locations are just pointing to the same document? Following is a snapshot of one of the links that I had tried:

Like Heleen_H, I tried both the Download button and the Download Manager button. I was hoping to verify today that it was still unaccessable but the site is almost completely unresponsive this morning. Everyone trying to download CS6 at once?
If these install instructions are the same as the link you posted to the online version then this is all pretty much a moot point but I just wanted to point out that it was the same problem in multiple locations.
Bill
This issue appears to have been resolved. My apologies for the diffculties. Can you please try downloading the instructions again?