how to fix the error 'Access-Control-Allow-Origin' sending POST with ajax?

I am sending a data through POST with ajax, but it never sends since I get that error "Access-Control-Allow-Origin" and I could not solve it, this is the code:

$.ajax({
      /*url: 'https://webto.salesforce.com/servlet/servlet.WebToLead',*/
      url: 'https://webto.salesforce.com/servlet/servlet.WebToLead',
      type: "POST",
      headers: {'Access-Control-Allow-Origin': 'https://webto.salesforce.com/servlet/servlet.WebToLead'},
      beforeSend: function (request) {
      request.setRequestHeader("Authorization", "Negotiate");
       },
      crossOrigin: true,
      crossDomain: true,
      data: {
        'first_name':datos[0]  ,
        'last_name': datos[1],
         'email': datos[2] ,
         'mobile': datos[3] ,
         '00N1I00000GF3OD':datos[4] ,
         'country': datos[5] ,
         'oid' : "00D1I000002KTso",
         'retURL' : "",
         'lead_source' : "Pagina Web",
         'recordType' : "0121I000000VktK"
      },
      success: function() {
         alert('termino1');
       }
    });

and I do not know what else to do '