Why can't' I download IOS 6.1.2 IPSW file

I'm trying to downgrade my iphone from IOS 6.1.3 to 6.1.2 but whenever I try to download a IPSW file instead of downloading it opens up another tab that loads forever or it will make it seem like its going to download but instead it makes the screen loads forever also. I've seen other people download IOS IPSW files without any problems but when I do it I get a screen that loads endlessly. I'm trying to jailbreak my phone but first I need to downgrade it.

I'm sorry to say you can no longer downgrade your handset to a lower iOS that the one that is being signed by Apple - ie 6.1.3.

Depending on your device, you can jailbreak on iOS6.1.3.

Check this site for genuine jailbreaks available; http://www.isthereajailbreak.com/