Ummm...just find any site that describes proper HTML syntax.

Briefly, HTML pages must be laid out like this:
...meta tags, etc, here are optional...
<style type="text/css">...</style>
You can put <script type="text/javascript">...</script> either in the <head> or in the <body>, though modern usage puts it in the <body> as the last thing just before the </body>.

If you use a <!DOCTYPE> (which you should), then the simplest to use is <!DOCTYPE html>. Doing so adds a couple of other restrictions on your HTML, but the w3c validator will tell you about them.

Note that you can have only *ONE* <body>...</body> pair.

Note that if you use a <form>....</form>, you can *NOT* next another <form>...</form> inside. (You can have multiple <form>s, but they can't be nested.)

There's more, but that will get you started.