Reusable code

Hi, I was wondering if there was a way that you can reuse code in HTML. I’m making a website and I have a side bar with navigation controls. This is going to be part of the standard look of the website. So I was wondering if there is a way to have this on every page without copying and pasting it on the each page? Sort of like in C-programming where you would create a module and call it with just 1 line of code.

I cannot use frames for this either because I have a javascript flyout menu in the sidebar which would get cut off by the edge of the frame.

Thank you.