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....