Request Method Changing from GET to OPTIONS alone

I have the following code:

$(function() {
    $('#method').change(function() {
        var method = $(this).val();
        if (method == 'GET' || method == 'DELETE')
            $('#json-group').hide();
        else
            $('#json-group').show();
    });

    $('#send-button').click(function() {
        var url = $('#url').val()
        var a = document.createElement('a');
        a.href = url;
        var method = $('#method').val();
        if (method == 'GET')
            var data = '';
        else
            var data = $.trim($('#json').val());
        var md5 = data ? CryptoJS.MD5(data).toString(CryptoJS.enc.Base64) : '';
        var date = (new Date()).toUTCString();

        var parts = [method, md5, date, a.pathname].join('\n');
        var hmac = CryptoJS.HmacSHA1(parts, $('#api_secret').val());
        var sig = hmac.toString(CryptoJS.enc.Base64);
        var auth = 'Zopim-Reseller-API ' + $('#api_token').val() + ':' + sig;
        var headers = {'API-Date': date, Authorization: auth};
         $.ajax({
      url: url,
      type: method,
      dataType: 'json',
      success: function() { alert('hello!'); },
      error: function() { alert('boo!'); },
      beforeSend: setHeader
         });

         function setHeader(xhr) {
    xhr.setRequestHeader('Authorization', auth);
    xhr.setRequestHeader('API-Date', date);
  }
    });
});

This code should send a GET request, but in Chrome it tells me the following data:

  

Remote Address: 67.23.229.9: 443
Request   URL: link
Request Method: OPTIONS   
Status Code: 200 OK
Request Headersview source
  Accept: /
Accept-Encoding: gzip, deflate, sdch
  Accept-Language: pt-BR, pt; q = 0.8, en-US; q = 0.6, en; q = 0.4
  Access-Control-Request-Headers: accept, authorization, api-date
  Access-Control-Request-Method: GET
Connection: keep-alive
  Host: reseller.zopim.com
Origin: link

And because of this error:

  

XMLHttpRequest can not load link . Request header field Authorization is not allowed by Access-Control-Allow-Headers.