If you’re using Internet Explorer, you probably saw a security warning dialog when you were trying to post your ad on Craigslist. This warning is triggered in Internet Explorer if it is displaying a secure HTTPS page that has caused a non-secure (i.e. HTTP based) resource to be downloaded.

Right before you post your ad on Craigslist you get a chance to preview your ad. Craigslist chose to deliver this preview page using a HTTPS connection but your ad (one of the elements of the preview page) is actually delivered using a HTTP connection.

Because some of the elements of the page are delivered using HTTPS and some using HTTP, Internet Explorer tells you “This page contains both secure and non-secure items“.

But I think that it’s not fair to say that anything being delivered in a normal HTTP connection is non-secure. The ads you created with GoGoPin Ad, delivered to viewers using a normal HTTP connection, are just plain PNG/JPEG images, which are completely safe, causing no harm to users at all.

Anyway, in Internet Explorer 7 and earlier version, this dialog would cause annoyance to users but generally didn’t cause any other significant problems. This was because it was worded in such a way that most users would click on the “Yes” button and allow non-secure content to be downloaded.

However, the wording in the IE 8 version of this dialog has changed:

Read carefully. Now you would have to click the “No” button to see all the content properly. Some of our users clicked the “Yes” button, saw nothing in the Preview page, and complained that GoGoPin Ad is not working properly. Well, I have to say that the dialog tricked them.

You won’t see this sort of warning dialog in Firefox or Safari. But if you are using Internet Explorer, please pay little bit more attention to what the dialog actually says.