Salsa automatically generates a secure URL for pages involving monetary transactions - donations, paid events, storefronts, etc.  However, just because those pages' URLs begin with "https://" doesn't mean they are secure - if you are loading nonsecure files or images anywhere on the "secure" page, the whole page will become nonsecure.  This manifests through a "broken" lock symbol in Firefox, and through pop-ups or other warnings in IE. You don't want potential donors or supporters scared away because they think their transactions won't be secure - so what you can do?

1.  Find out which template your nonsecure-soon-to-be-secure page is using.  You can do this by looking at  the number after the /t/ in the page's URL - this is the template key - or checking  which template is highlighted on Step 1 of your page creation workflow.  If no template is highlighted or there is no /t/ in your URL, you're using your site's default template. To see a list of your templates, go to dashboard -> manage templates.