Apply jQuery to elements created by ajax - ajax

Question

I'm trying to figure out how to apply jQuery methods, functions etc for elements that have been created with ajax.
In my page there is a dropdown list #cat_id and depending on the selection made, a set of UL elements are created. I then need to call the following function for each element created:
$('#allowSpacesTagsX').tagit({ itemName: 'itemX', fieldName: 'tagsX', availableTags: sampleTagsX, allowSpaces: true });
where allowSpacesTagsX (X=1,2,3,....) is the id of the created UL elements. This method binds the UL to an auto-complete tagging widget similar to the tagging element used in StackOverflow.
Normally the code above would be included in the document.ready for the static elements but I need to add it for each element created with ajax.
This is a small sample of code to understand my question better:
<script src="../js/tag-it.js" type="text/javascript"></script>
<script>
$(document).ready(function() {
$('#cat_id').live('change', function(e){
$.post('../includes/ajax.php', {
cat_id : $(this).find("option:selected").attr('value')}, function(data) {
$("#tagholder").html(data);
});
});
});
</script>
Edit:
example added to demonstrate an example of the code that should be produced:
$(function(){ // Creates the arrays of tags to be assigned to each tag field
var sampleTags1 = ['USB', 'DVB', 'GSM', 'OEM'];
var sampleTags2 = ['Alfa Romeo', 'Audi', 'Chevrolet', 'Mazda', 'Mercedes'];
var sampleTags3 = ['20cm', '21cm', '8in'];
$('#allowSpacesTags1').tagit({ itemName: 'item1', fieldName: 'tags1', availableTags: sampleTags1, allowSpaces: true });
$('#allowSpacesTags2').tagit({ itemName: 'item2', fieldName: 'tags2', availableTags: sampleTags2, allowSpaces: true });
$('#allowSpacesTags3').tagit({ itemName: 'item3', fieldName: 'tags3', availableTags: sampleTags3, allowSpaces: true });
});

Answer 1

<script src="../js/tag-it.js" type="text/javascript"></script>
<script>
$(document).ready(function() {
$('#cat_id').live('change', function(e){
$.post('../includes/ajax.php', {
cat_id : $(this).find("option:selected").attr('value')},
function(data) {
$("#tagholder").html(data);//places your ajax content
//grab that element again and then apply any jquery function to it
//example add a class to an arbitary h1 tag inside #tagholder
$("#tagholder h1").css('class','heading');//like so
});
});
});
</script>