js调用web api登录问题

先写了一个简单的js测试下能不能通过js调用web api登录系统，但是显示有问题：
XMLHttpRequest cannot load http://win-pmqesug7uo0/K3Cloud/Kingdee.BOS.WebApi.ServicesStub.AuthService.ValidateUser.common.kdsvc. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.
js的代码如下：
function LoginCloud()
{
var cloudurl="http://win-pmqesug7uo0/K3Cloud/Kingdee.BOS.WebApi.ServicesStub.AuthService.ValidateUser.common.kdsvc";
var loginJson=
{ "format": 1,
"useragent": "ApiClient",
"rid": "",
"parameters": "[\"57a40d3e590ec4\",\"kingdee\",\"888888\",2052]",
"timestamp": "",
"v": "1.0"
}
var myDate = new Date();
var guid = newGuid();
loginJson.timestamp=myDate.getTime().toString();
loginJson.rid=guid;
var jsonstr=JSON.stringify(loginJson);
alert(jsonstr);
$.ajax({
type: 'post',
url: cloudurl,
data: jsonstr,
contentType: "application/json; charset=utf-8",
dataType: 'json',
success: function(data) {
alert("Success");
},
error: function (e) {
alert(JSON.stringify(e));
}
});
}