[Answer]-Why is my Django jQuery button not working?

there was a small (but significant!) bug in your code

"'/photo/like/'+ post_id" is incorrect, you want "/photo/like/" + post_id. notice it isn’t all surrounded by quotes

Ok I manged to get in work like this:

photo.html:

{% if pic %}


<script>
$(document).ready(function(){

    $('#like').click(function() {

        var $this = $(this);
        var post_id = {{pic.id}};

        $.ajax({
            type: "POST",
            url: "/photo/like/" + post_id ,
            data: { 
        'pic_id': post_id,
                'csrfmiddlewaretoken' : $("input[name=csrfmiddlewaretoken]").val()
            },
            success: likeSuccess,
            dataType: 'html'    
        });            
    });    
});

function likeSuccess(data, textStatus, jqXHR)
{     
    $('#likes').html(data);
}

</script>

<img class="pic" src="/static/assets/{{pic}}" />
<br />

{% csrf_token %}
<input type="button" id="like" name="like" value="Like" />

<p id="likes"> {{pic.likes}} &nbsp;liked this </p>

{% endif %}

views.py

def like_photo(request, pic_id):
    if request.method == 'POST':
        if pic_id:
            uid = request.user.id
            p=UserPic.objects.get(id=pic_id)

            #if UserPic.objects.filter(liked_by__user__contains=uid):
            if Liker.objects.filter(user=uid, pic=pic_id):
                #return HttpResponse('You have already liked!')

                p.likes -=1
                p.save()
                Liker.objects.filter(user= uid, pic=pic_id).delete()
            else:

                p.likes +=1
                p.save()
                newliker = Liker(user= uid, pic=pic_id)
                newliker.save()

            args = {}
            args.update(csrf(request))
            args['likes'] = p.likes

        return render_to_response('userpics/likes.html', args)

also needed to create a specific html for ajax call:

likes.html

{% if likes > 0 %}
{{likes}} liked this
{% else %}
crap
{% endif %}  

Not sure if it is the best way but it works.
I wish I could use a more elegant json to return the likes digit and get rid of the likes.html but could not figure out how to do so.

Also, for some strange reason the script does not work when I import it externally at base.html:

<script src="{% static "assets/js/likes.js" %}"></script>

though firebug says that it is loaded on the page.

Your suggestions to improve the answer are welcomed.