It’s pretty often that we use and see relative URL’s. They are everywhere. They help maintain portable environments and organization / maintenance of websites. What many may not hear about that often are that URL’s can also have relative protocols. Since IE7, browsers allow you to create a link beginning with a double forward slash “//” that acts as a relative protocol. This ensures that you maintain a single protocol throughout a single session. For example, switching from HTTPS to HTTP in IE7 and IE8, you will get a security warning that is extremely intrusive to a users experience. Take a look at some examples.
Now there have been issues with browsers, specifically IE6. But it’s safe to say that IE6 can be dropped off, within the past year, especially in the United States, less than 2%. Chinese websites still get a significant IE6 present, but still less than 20%. All-in-all, this Relative Protocol URL is very effective and perfect for cross protocol situations, commonly used in cross-domain situations. Enjoy!