回声标记（文本）在页面上不可见

I added a simple php echo tag on my website:

<?php echo "Test"; ?>

This message schould be displayed above the header (wich has a green background. The header moves a little, but I can't see the text "Test". Then I tried this code:

<?php echo "<h1>Test</h1>"; ?>

Again, the header moves a little more, but the text is invisible.

First:

After the normal echo tag:

After adding h1:

Can you help me?

Your PHP echo needs to be inside the HTML body element to be displayed on the page. Everything else you see is a result of the browser attempting to correct invalid HTML (which can look very different between different browsers).