You don't need an onclick. Assuming you're using Bootstrap 3 Bootstrap 3 Documentation
<div class="span4 proj-div" data-toggle="modal" data-target="#GSCCModal">Clickable content, graphics, whatever</div>
<div id="GSCCModal" class="modal fade" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
<div class="modal-dialog">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-hidden="true">× </button>
<h4 class="modal-title" id="myModalLabel">Modal title</h4>
</div>
<div class="modal-body">
...
</div>
<div class="modal-footer">
<button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
<button type="button" class="btn btn-primary">Save changes</button>
</div>
</div>
</div>
</div>
If you're using Bootstrap 2, you'd follow the markup here: http://getbootstrap.com/2.3.2/javascript.html#modals