Images don't show, appear blank. Error in mootools or slimbox?

[Txell]

Hello,

First of all, thank you in advance for helping me, as I'm not a big code developer and I'm getting desperated with this issue on my website: www.elbrogit.com. I just can't see the images when I click on them, neither on the main page nor in any activity post, there always appear a blank window. I've tried to understand the code of slimbox and mootools, but, after several hours, I had to give up, can't figure out how can I make it work. It seems to me it might be an error on getting the url, but when I right click on the image and choose to "open image in new window", I can see it. 

I will really thank you a lot if you could help me solving this issue, as I'm getting quite desperate by now. 

Meritxell, from Catalonia.