tabpanel加载页面无法显示

var tabs = new Ext.TabPanel({
            region: 'center',
            deferredRender:false,
            monitorResize: true,
            enableTabScroll:true,
            //frame:true,
            margins:'3 3 3 0',
            activeTab: 0,
            defaults:{autoScroll:true},

            items:[{
                title: 'Bogus Tab',
                //body:new Ext.ux.ManagedIFrame({autoCreate:{ src:"hello.html", frameBorder: 0, cls:'x-panel-body',width: '100%', height: '100%'}})
                //iconCls:'tabs',
                //html: Ext.example.bogusMarkup
                autoLoad:'hello.html'
            },{
                title: 'Another Tab',
                //html: Ext.example.bogusMarkup
                autoLoad:'layout_test.html'
            },{
                title: 'Closable Tab',
                html: Ext.example.bogusMarkup,
                closable:true
            }]
        });



”tabpanel中加载hello.html页面，则在“tabpanel”窗口无显示，但文本文字可以显示，而单独访问hello.html页面则正常