Hi Cristián,
As I promised I’ll tell you the solution.
Striking has a great range of options. Especially the new Striking responsive, which I use at the moment. The truth is that I still don’t know the full possibilities of this theme. Therefore I make many mistakes, as I did with the s2M’s widget.
Striking has options to set different colours for different elements of the website. Including a colour for the footer feeds.I changed the colour from white to black and now I’m able to use the widget without any problem.
That’s good :)
Still no explanation why I was able to use it without any problem on all browsers except Mozilla and why Mozilla didn’t have problem with the sidebar’s widget, but i don’t care for now :D
I’m happy :)
Thank you so much for your support, Cristián!
Best,
Prolet