Lang is undefined error & script file error


I have 2 errors coming up on my website, and would be grateful if anyone can help. My website concerned is

  1. My web designer added the 4th line below (

    2) When you load the homepage, you get an error on the bottom right of the window (Done but with errors on page). After you click on this, it tells you the error is : 'lang is undefined' line 12, char 3 ajax.js . Any idea why this error is occurring & what i can do to fix it?

    Many thanks