Hi Marcos,
Microsoft just retired many of its Seadragon-related websites, including seadragon.com, and unfortunately, your site was linking to Seadragon Ajax (seadragon-min.js) on seadragon.com.
Fortunately, hope is not lost! You can still (and it's been recommended for the past couple of years to) host the Seadragon Ajax files yourself, so you don't need to depend on any Microsoft servers.
You can find all the relevant files here:
https://github.com/aseemk/seadragon-ajax
You should be able to drop these files directly into the same folder as your HTML, and link to the local seadragon-min.js, and hopefully everything should "just work". =)
Also FYI that these days, there is a new open-source project that continues building on this stuff (and so is more feature-rich now) called OpenSeadragon:
http://openseadragon.github.io/
It's not a drop-in replacement for Seadragon Ajax, but if you're making these changes anyway, you might like to switch over to that while you're at it. =)
I'm sorry for your inconvenience, but I hope this all helps!
Cheers,
Aseem