Cannot see preview of pictures on certain websites

[Dumb and Dumber]

I could always see the thumbnails of the magazines on sites where you can download them in PDF format.
But I had to reload Windows as I got a new motherboard. Now suddenly I cannot see the thumbnails on this specific site anymore. ''http://www.downmagaz.com''
Previously Firefox was like this, but through Windows Explorer I could get it right. Now not one of the two want to show me the thumbnails.
What can I do about this?
I did install flash player and Adope Reader.

 

[Micron]

 

[Dumb and Dumber]

 

[Hi-Fi Geek]

 

[Dingbat]