How do i fix this error that comes up when i load any page 

the app you suggested completely removed all js, i had to revert back to a previous code because it removed more than what was needed

I am doing all this myself, I did find that my theme was not up to date, so that has helped. Now to continue fixing what pagespeed shows has issues.

How can I fix this error dealing with 404, shows up on all pages 

Attempting to close HtmlElement 'a' before HtmlElement 'div' was closed is what the red lines are saying.  Attempting to close HtmlElement 'div' before HtmlElement 'body' was closed is what the red lines are saying.