In my web application I got Header.jsp file which contains default header contents. Im including it in all other pages using jsp:include tag inside body tag of each individual p
As per W3C standards, you can not have two HEAD tags.
Concerning your issue, you can call header.jsp file without HEAD tag or may be you can rename to scripts.jsp or constants.jsp
For example:
Header.jsp
Main.jsp
Main page ..... other HTML contents specific to main page .....