html header/library file

I wanted to create something like C library but for html code to be included in html or aspx html portion. How do I do that? Thanks in advance.Write the code in .inc file and include those where ever u want

Devendra Naik.
what's the exact command to include the .inc file?
I used <!--#include virtual="topnav.inc"--
but it doesn't seems to work.
Anyone??