What effect does prefixing a title attribute with "blocked::" have on a link?

I have noticed that some websites prefix the titles of their links with blocked::.

For example:

<a href="http://www.a-url.com" title="blocked::http://www.a-url.com">www.a-url.com</a>

I have questions about how this affects browsers and search engines:

1. Is this meant to have some effect on the browser? If so, what is the intended effect and does it work?
2. Is this meant to have an effe开发者_高级运维ct on search engines? Is it similar to a no follow link or does it not have any effect on search engines at all?

I have never seen this kind of syntax, and I'm quite sure it has no standardized meaning.

However, interestingly, Microsoft Outlook marks the href part of links this way as a security feature:

When you receive an HTML message, links in it may not work or the File, Open dialog will open, asking to associate an executable file with the link.

Looking at the source, you'll see the URL is prefixed with BLOCKED::, like this:

<A title=http://office.microsoft.com/ href="BLOCKED::http://office.microsoft.com/">Office Online</a>

This is a security feature in Outlook and may happen when URLs are copied from one email message and pasted into another message.

My guess would be that those links are actually copy+pasted links from a Microsoft Office document, and the title element somehow gets garbled in the process.

Is it possible that this tag is not actually part of the web page, but is being inserted by your firewall software?