i have two files about.jsp and contactus.jsp

in this both file i have included header.jsp and left.jsp and footer.jsp
using <%@ include file="" %> tag

i compiled contactus.jsp and it is working fine, when i was working on about.jsp i made some changes in left.jsp file ..... when i see about.jsp this changes in left.jsp show up but when i see contactus.jsp the old left.jsp file is displayed ? why ?

if this persist , and if i make changes in one file which i included every where then it wont show up changes every where ? what to do? pls help?