My a href tag on image doesn't work when the site is resized to a smaller width

Question

Here is the site: http://boceski.16mb.com/
I have images from flags in the top left angle of the page.
When I click the image, it changes the text to other language. The images are clickable and I can change the language when I view them on my normal screen, but when I resize the website or when I open the website from mobile, I can't change the language. It doesn't read the <a href=""> tag. I don't know why, Can you please help me??

Answer 1

Add z-index: 2 into de CSS to the .header rule.

Recomendation: Make flags images bigger to get a better user experience in mobile context.