First of all, when you say “version of js” you really mean “version of jq, or jQuery”. jQuery is built on JS but it’s weird to say “version of js” because that’s a whole other deal. But, maybe it was just a typo. :)
Yep, the jQuery dollar variable ($) is undefined on your site. Taking a closer look, it seems that the jQuery script that you have included is not identical to the one on, for example,
Look at the very bottom of your jQuery file
http://marensblog.dk/wp-includes/js/jquery/jquery.js That last line that says
Did you add this line? It is what’s causing these errors, because it tells jQuery to “forget” about the $ variable by setting it to whatever value it had before jQuery was loaded, in your case undefined.
Long story short: Remove that last line from your jquery.js file.