Did you know that if this line is in the <head> section of your template:
<link rel="stylesheet" href="index.php?id=29" type="text/css" media="screen" />
and resource 29 contains a snippet tag, that snippet will execute for every page that uses the template?
I don’t recommend doing this on purpose, but it’s an interesting little fact. I have no idea how the line got into my template. My best guess is that I was experimenting with putting CSS in a resource, later repurposed the page with the CSS to test QuickEmail, and forgot to remove the line from the template.
I might never have known about it except that the snippet with its tag on resource 29 sends me an email. I got about 30 emails before I finally figured out what was happening.