Add HTML code outside content area on every page load
Content is a region in your theme. Site content goes into regions. So, typically you can only put things in defined regions such as Header, Footer, Left Sidebar, Content.

You have slight flexibility with #prefix and #suffix render array attributes. You either have to edit the html.tpl.php file, or define your own region within a theme. Or you can supply your own hook_theme() implementation to hint when using your own html.tpl.php template file.