Beauty is in the eye of the beholder, or something...

ajaxtester.coffee

testScadaTag = ->
    $("#tagTest").attr("src", "/Content/blank.gif");
    if (viewModel.scadaTag())
        $("#tagTest").attr("src", "/Content/smallSpinner.gif")
        $.ajax
            url: "/Scada/Test/#{viewModel.scadaTag()}"
            type: 'POST'
            dataType: 'json'
            error: (jqXHR, textStatus, errorThrown) ->
                $("#tagTest").attr("src", "/Content/fail.png")
            success: (data, textStatus, jqXHR) ->
                $("#tagTest").attr("src", "/Content/ok.png")