You are in APEX4.2 version. You can try to use built-in Dynamic Action (in other word: AJAX functionality) in APEX. Please refer the below link,
Hope It will help and make it in simple way..
What Jari said: apex.server.process cuts down on code and implements jquery post very well. That said, I think the problem with your call specifically is your request value. It should be
"p_request" : "APPLICATION_PROCESS=SAVE",
similar as to what you provided in htmldb_Get. Just passing "SAVE" will not call a process with that name.
Another good idea is to check things in your browser. Inspect the ajax calls made, see what you pass on and see what is returned. In firefox+firebug you can see ajax calls in the console tab, in Chrome you need to check the network tab, and in ie (9 and up) you need to manually start the capture from the network tab. In any case the developer tools have to be opened in order to capture. You can just run your call from the console and then check the ajax call. Then check the call's headers. That is simply the best way to debug ajax calls.