jQuery Official Doc.

<script src="http://www.google.com/jsapi"></script>
<script>
    // Load jQuery
    google.load("jquery", "1.2.6");
</script>
<script>    
    $(function() {
        //apply mouseover handlers
        $("#map_rating_choices area").mouseover(function(e){
            e.preventDefault();
            $("#rating_choices").attr("src","/i/stars"+$(this).attr("value")+".gif");
        });
        
        //apply click handlers
        $("#map_rating_choices area").click(function(e){
            // stop normal link click
            e.preventDefault();
            
            // send request
            $.ajax({
                type: "POST",
                url: "wwv_flow.show",
                data: {p_arg_names:"P2_RATING", 
                       p_arg_values:$(this).attr("value"), 
                       p_flow_id:$('#pFlowId').attr("value"), 
                       p_flow_step_id:$('#pFlowStepId').attr("value"), 
                       p_instance:$('#pInstance').attr("value"), 
                       p_request:"APPLICATION_PROCESS=NEW_RATING"
                },
                dataType: "json",
                success: function(data, textStatus){
                    $("#rating").html(
                            "Thanks for rating, current average: " +
                            '<img src="/i/stars'+data[0].average+'.gif" alt="'+data[0].average+'" />'+
                            ", number of votes: " +
                            data[0].count
                        );
                }
            });
        });
    });  
</script>

DECLARE
    l_rating    NUMBER := to_number(:P2_RATING);
    l_retval    VARCHAR2(32767);    
    l_average   NUMBER;
    l_count     NUMBER;   
BEGIN
    INSERT INTO JQ_RATINGS(rating) VALUES(l_rating);    
    COMMIT;
    
    SELECT  round(avg(rating))
           ,count(*)
    INTO    l_average
           ,l_count 
    FROM    jq_ratings;
    
    l_retval := '[{''average'':'''||l_average||''',''count'':'''||l_count||'''}]';
    
    htp.prn(l_retval);
EXCEPTION
    WHEN others THEN
        htp.prn('');
END;