In small browser window left sidebar jumps down

Theme I’m using is Twenty Fourteen, and I’ve made a child-theme of it.

I’m having troubles with the left sidebar of my website. When I’m using my laptop, the window is smaller then on my desktop. It looks fine on my desktop, but when wathing it on my laptop the left sidebar jumps down my content box.

I know the content of my page is the #primary div and the left sidebar the #secondary, the first pushes down the second when window is smaller. But how can I prevent this? I don’t want neither of them to jump anyware, just stay put… can someone help me?

This is the url of the website: http://31.3.97.74/~drillm/

Thanks in advance!