$.getJSON() sets the dataType as JSON, you should set dataType: 'html' using $.ajax instead.
Something like this:
$.ajax({
url: 'myurl',
dataType: 'html',
success: function(selectMarkup) {
$('#my_div_id').html(selectMarkup);
}
});
What is dataType property? Here is the description from jquery Docs:
Data Types
The $.ajax() function relies on the server to provide information about the retrieved data. If the server reports the return data as XML, the result can be traversed using normal XML methods or jQuery's selectors. If another type is detected, such as HTML in the example above, the data is treated as text.
Different data handling can be achieved by using the dataType option. Besides plain xml, the dataType can be html, json, jsonp, script, or text.