Developing ui using Ext-js

I m new to Ext-js .I m developing a form.but not able to alli开发者_StackOverflow中文版gn it to center. This is my code

Ext.onReady(function()
{

    Ext.QuickTips.init();
    Ext.form.Field.prototype.msgTarget = 'side';



  var reg_form = new Ext.FormPanel({
  renderTo: document.body,
  title: 'Employee Registration Form',
  width:600,
  height:500,
  bodyStyle: 'padding:10px 10px 15px 15px;background:#dfe8f6;',
  items: [

  {

    xtype: 'numberfield',
    fieldLabel: 'Employee Id',
    name: 'id',
    decimalPrecision:2,
    allowBlank: false
  },
  {

    xtype: 'textfield',
    fieldLabel: 'Employee Name',
    name: 'name',
    allowBlank: false,
     vtype:'alpha'

  }
]
 });

});

Thank you in advanced.

---

You'll need to apply css to do that, or use the x & y configs of formpanel

---

One more way to solve this problem: use

Ext.Window({
     maximizeble : false, 
     resizeble : false,
     closable: false, 
     minimizeble: false,
     ...
})