How to Avoid Bad Requests? Site Speed issues

Hello,

Recently my site: http://www.youngster.co.il was having some serious speed issues, loading times went up high.

When I run a speed test in Gmetrix, Pingdom etc I spotted the following:

“Avoid bad requests”

The following requests are returning 404/410 responses. Either fix the broken links, or remove the references to the non-existent resources.

http://www.youngster.co.il/none

I’ve tried locating the broken link/reference but I didn’t manage to find it. I’ve been reading online and haven’t found anything that really helped me out.

My first question would be what’s causing this error and how to fix it?

Second, do you believe this is what’s breaking my site’s load time?

I would appreciate any input as I’ve been fighting and struggling with my site’s speed for a long time.