SHOW HIDE DIV

<div id='content'>Hello World</div>
<input type='button' id='hideshow' value='hide/show'>

jQuery:

jQuery(document).ready(function(){
    jQuery('#hideshow').live('click', function(event) {        
         jQuery('#content').toggle('show');
    });
});

For versions of jQuery 1.7 and newer use

jQuery(document).ready(function(){
        jQuery('#hideshow').on('click', function(event) {        
             jQuery('#content').toggle('show');
        });
    });