.html file is not working in spring3

Question

I am developing spring mvc application using spring3.0 my web.xml file is as below

Spring.xml

<display-name>Spring3MVC</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>/</url-pattern>
</servlet-mapping>

spring-servelet.xml

<context:component-scan
    base-package="com.asset" />

 <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">  
    <property name="prefix" value="/WEB-INF/jsp/" />  
    <property name="suffix" value=".jsp" />  
</bean>  

when I run my project it give 404 resource not found exception.

but If I use index.jsp as welcome page its work and index page is appear.

So can you Please comment why .html is not working as welcome page.