[jquery] Calling jQuery method from onClick attribute in HTML

this works....

<script language="javascript">
    (function($) {
     $.fn.MessageBox = function(msg) {
       return this.each(function(){
         alert(msg);
       })
     };
    })(jQuery);? 
</script>

.

   <body>
      <div class="Title">Welcome!</div>
     <input type="button" value="ahaha"  onclick="$(this).MessageBox('msg');" />
    </body>

edit

you are using a failsafe jQuery code using the $ alias... it should be written like:

(function($) {
  // plugin code here, use $ as much as you like
})(jQuery); 

or

jQuery(function($) {
   // your code using $ alias here
 });

note that it has a 'jQuery' word in each of it....