What does the "base href" meta tag do? For SEO and webdesign?

[jmansd]

I have encounter the "base href" on one of my sites.  The tag is on every page and always points to the home URL.

[AdoptionHelp]

<base> allows you to set the default attributes for links on the page. For example if I set <base href="http://www.mydomain.com/"> then I can make a link to and it will point to http://www.mydomain.com/mypage.html

I believe this magic happens on the web server before the page is sent to the browser, making it a safe practice for SEO.