在IDEA修改了web.xml后，点击浏览器图标就没反应了？

Question

web.xml代码：<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"          xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"          version="4.0" metadata-complete="true">     <servlet>         <servlet-name>registerServlet</servlet-name>         <servlet-class>servlet.HelloServlet</servlet-class>     </servlet>     <servlet-mapping>         <servlet-name>registerServlet</servlet-name>         <url-pattern>/servlet/HelloServlet</url-pattern>     </servlet-mapping>     <welcome-file-list>         <welcome-file>index.jsp</welcome-file>     </welcome-file-list> </web-app>项目路径：