1 eclipse Installed JREs should use jdk not jre
2 when renew a server,we should choose the jdk for jres
3 if we want to access apache root page,we should double-click the server,choose
  "takes control of Tomcat" in the "Server Locations" part and set Deploy path 
  with "webapps".
4 run the new server in servers window(
Program arguments : start
VM arguments :
-Dcatalina.base="D:\Program Files\Java\.metadata\.plugins\org.eclipse.wst.server.core\tmp1" -Dcatalina.home="E:\Program Files\Apache Software Foundation\Tomcat 7.0" -Dwtp.deploy="D:\Program Files\Java\.metadata\.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps" -Djava.endorsed.dirs="E:\Program Files\Apache Software Foundation\Tomcat 7.0\endorsed")
5 attach webapps to its model(<Context docBase="dynamicTwo" path="/dynamicTwo" reloadable="true" source="org.eclipse.jst.jee.server:dynamicTwo"/> under Host tag of server.xml),then run webapps on this server