1. 如果JSONP返回的Content-Type不符合规范，那么请求将出现了被IE9 block掉的情况；
2. 在IE9中，如果在Jsonp请求中，http response header中有X-Content-Type-Options: nosniff并且Content-Type: text/html; charset=GBK那么这个请求的内容不会被IE9当成 javascript执行。
IE9可执行脚本mime-type：
"text/javascript", "application/javascript", "text/ecmascript", "application/ecmascript", "text/x-javascript", "application/x-javascript", "text/jscript", "text/vbscript", "text/vbs"
text/javascript与application/javascript的区别：
application/javascript: JavaScript; Defined in RFC 4329 but not accepted in IE 8 or earlier, however text/javascript is accepted.
text/javascript (Obsolete): JavaScript; Defined in and obsoleted by RFC 4329 in order to discourage its usage in favor of application/javascript. However,text/javascript is allowed in HTML 4 and 5 and, unlike application/javascript, has cross-browser support