jQuery ajax call errors in IE8

You're getting a 411 response from your service:

411 Length Required

The server refuses to accept the request without a defined Content- Length. The client MAY repeat the request if it adds a valid Content-Length header field containing the length of the message-body in the request message.

This is because jQuery does not set the content-length header when posting if there is no data. This is a security requirement when posting to IIS:

The underlying issue is that most installations of IIS6+ require a content-length be provided with all POST requests, even if there is no content (POST data).

The content-length for a request with no data should be 0, but jQuery doesn’t set that header automatically unless there is a data parameter. Since ASP.NET AJAX’s JSON serialized services require a POST request, this becomes a stumbling block for read-only requests.

(Quoted from from http://encosia.com/3-mistakes-to-avoid-when-using-jquery-with-aspnet-ajax/)

Simply setting the data parameter to an empty objects seems the simplest workaround:

$.ajax({ url: '/base/RoomBuilder/GetRoomShape.aspx?_='+d.getTime(), async: false, type: 'post', cache: false, data: "{}", dataType: 'html', success: function(data){ if(data.substring(0,5) == 'Error'){ alert('Please select a room shape to continue'); blnError = true; }else{ roomShape = data; } }