Try this (see a working example of this code in jsfiddle: http://jsfiddle.net/periklis/7ATLS/1/)

<input type = button id = clickme value=Click me!/>

<div id = alert_placeholder></div>

<script>

bootstrap_alert = function() {}

bootstrap_alert.warning = function(message) {

            $('#alert_placeholder').html('<div class=alert><a class=close data-dismiss=alert>×</a><span>'+message+'</span></div>')

        }



$('#clickme').on('click', function() {

            bootstrap_alert.warning('Your text goes here');

});

</script>​

EDIT: There are now libraries that simplify and streamline this process, such as bootbox.js