Pop advertisement in ojs web

I have a problem, my ojs web always gives me a pop-up advertisement in any computer browser I use. please check in http://jurnal.kimia.fmipa.unmul.ac.id/index.php/JKM
if i click menu in my website… always redirected to ad.fly link or pop-up advertisement

I wasn’t able to replicate this. Does this happen on any browser on one computer, or does it happen on multiple computers? Can you give an example with screenshots and the exact steps you take?