How to repeat a code in html without writing the same code again and again

Well I wish to show a given piece of code multiple times on a given page but I wish to minimize the redundant code being repeated everywhere (simple copy/paste) . Well I heard of people using Javascript or JQuery to store the given piece of code say HTML or CSS and than they use some simple div renders or the <!--data--> tag multiple number of times in wherever place they want the code to appear, which I have no idea how to use that is store a info in the scripts or html and then render it multiple number of places with a single div or comment.

Can anyone illustrate how to do this with an example. A bit more info on such tricks will be very resourceful.


Have a look at server side includes

Include it like this in your page :

<?php include ('content.html'); ?>