关于Ext.BLANK_IMAGE_URL

在ExtJS中BLANK_IMAGE_URL是

BLANK_IMAGE_URL : (isIE6 || isIE7) ? '/' + '/www.sencha.com/s.gif' : 'data:image/gif;base64,R0lGODlhAQABAID/AMDAwAAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw=='

IE6,IE7不支持url内嵌base64编码数据的图片,默认从www.sencha.com/s.gif下载图片，因此需要修改Ext.BLANK_IMAGE_URL从本地下载图片

if (Ext.BLANK_IMAGE_URL.substr(0, 4) != "data") {
Ext.BLANK_IMAGE_URL = "/ExtJS/resources/themes/images/default/s.gif";
}