Use server-side includes, if your server supports them. Ask
your Webmaster if this is the case, and if so, what the
exact syntax is for your server.

Since server-side includes make the document slower, they
are not always desirable. If your documents only have a
static footer, which doesn't change every day, you might be
better off by using an editor which can insert files in the
current document, or a preprocessor. The C preprocessor can
do this, but there are also several HTML-specific
preprocessors available. I recommend