Fotiman - 11:55 pm on Feb 7, 2013 (gmt 0)
That is your success handler... the result of your POST. msg contains the data returned, so you could inspect that to see what was actually received. Most browsers today include developer tools that allow you to set breakpoints and inspect data at runtime. For example, in Chrome you can press F12 to open the Developer Tools, then find that line in the code and add a breakpoint. Then add the msg to the watch list.
Alternatively, you could do something like alert(msg) ;)