In IE7 my web site always causes the browser to prompt a ‘Security Information’ dialogue box:
This page contains both secure and non-secure items.
Do you want to display the non-secure items?
How can I avoid getting this message when traveling between non-secure and secure pages (HTTP to HTTPS)?
You need to make sure all your images, script files, CSS files and so on have HTTPS urls if you’re on a secure page.
If you view-source and search for ‘http:’ this will soon tell which one (or more) is wrong.
Example: