Just go with this example, http://mattberseth2.com/master_detail_example/ , In this demo, when I enter any html code(or just even a "<"), will cause a 500 error from server.
Do the following, you will know what I am saying.
eg. when first time click "details" button, in any textbox(eg. in City texbox, enter "<b>") and click no matter "Save" or "Close". And then click on any "details" button again, then, you will see the error.
How/why this happens?