The content of element type "web-app" must match "(icon?,display-name?,description?,distributable?,context-param*,filter*,filter- mapping*,listener*,servlet*,servlet-mapping*,session-config?,mime-mapping*,welcome-file-list?,error-page*,taglib*,resource-env- ref*,resource-ref*,security-constraint*,login-config?,security-role*,env-entry*,ejb-ref*,ejb-local-ref*)".

SOLUTION

This is my web.xml file

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>
  
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>
  
  <servlet>
      <servlet-name>spring</servlet-name>
      <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
      <load-on-startup>1</load-on-startup>
  </servlet>
  
  <servlet-mapping>
      <servlet-name>spring</servlet-name>
      <url-pattern>*.html</url-pattern>
  </servlet-mapping>

</web-app>


Now in the error it is mentioned that web-app should contain element in the order as follows
eg)As per the order mentioned in the error web-app must contain <servlet> tag first, then <servlet-mapping> and after that <welcome-file-list>


so just we have to change the position of the <welcome-file-list> tag as follows.so the required web.xml file must be as follows

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>
  
  <servlet>
      <servlet-name>spring</servlet-name>
      <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
      <load-on-startup>1</load-on-startup>
  </servlet>
  
  <servlet-mapping>
      <servlet-name>spring</servlet-name>
      <url-pattern>*.html</url-pattern>
  </servlet-mapping>
  
    <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>

</web-app>