can I include external html code into my index.html?

essentially (shorthand)
----------------------------------------------------
INDEX.HTML
----------------------------------------------------
<html>
<body>
<h1>Text example 1</h1>
<p>Here is a list that will change daily on many pages.</p>

<!-- This is the syntax I am searching for. I need to repeatedly change this section on multiple pages -->

<??>insert.html</??>

</body>
</html>

----------------------------------------------------
INSERT.HTML (or maybe even just TXT?)
----------------------------------------------------
<!-- Even though I used them here, I am guessing no body or html tags as I dont want to insert them into the code above?? Not sure, I just want this code to embed or patch into the index at the proposed spot somehow, so I can open only this file and make edits and instantly update the other pages all at once. -->

<html>
<body>
<ul>
<li><p>item 1</p></li>
<li><p>item 1</p></li>
<li><p>item 1</p></li>
</ul>
</body>
</html>

----------------------------------------------------

God2015-11-30T21:58:08Z

That depends on the webserver being used. Some (Apache, IIS) support server-side include directives, but they must be enabled.

Chris2015-12-01T04:15:16Z

A much much better way is to use PHP.