Web. XML error

When writing Web. XML, I always reported cvc-complex-type.2.4.a:invalid content was found starting with element error, also appeared small Red Fork, found a lot on the internet, It is said that the Red Fork code written in between <jsp-config></jsp-config>, after trying to find completely useless.
Later found a method on the foreign language website to solve the problem
Workaround Two:

<async-supported>true</async-supported> is a new feature of Web. XML 3.0, just

<web-app xmlns:xsi= "http://www.w3.org/2001/XMLSchema-instance" xmlns= "Http://Java.sun.com/xml/ns/javaee" xsi: schemalocation= "Http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id= "Webapp_ ID "version=" 2.5 ">

Change to:

<web-app xmlns:xsi= "http://www.w3.org/2001/XMLSchema-instance" xmlns= "Http://java.sun.com/xml/ns/javaee" xsi: schemalocation= "Http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id= "Webapp_ ID "version=" 3.0 ">
can be resolved.

Web. XML error