index.php
Assign the href as list item values in drop down. Onchange of dropdown, make the ajax call.
class name "ajax" is just for reference (useful, if you want to handle event for morethan one element).
Change your code like this:
jQuery('#dropdown_id').live('change', function(event) {
jQuery.getJSON($(this).val(), function(snippets) {
for(var id in snippets) {
// updated to deal with any type of HTML
jQuery('#' + id).html(snippets[id]);
}
});
});
And your dropdown should look like this:
<select id="dropdown_id">
<option value="one.php">One</option>
<option value="two.php">Two</option>
</select>