URL tags are tags that somehow use or manipulate the URL or HTTP headers. Among other things they manipulate;

prestate options

Prestate options are a way to present options in the URL, that will be persistent for a user over several pages. A prestate for the options txt and en would be stored as http://www.roxen.com/(en,txt)/my.page in the URL. If you use prestate options you must only use relative URLs in your links.

cookies

Cookies are a way for a web site to store a small amount of information in the users' browsers. It is a much better way than prestates to handle information that should be persistent for a user over several pages.

authentification

HTTP can be used to transmit a user name and a password through HTTP.

expire

It is possible to tell the browser, and any proxy on the way to it, how long it is to cache a page.

<apre>

Adds or removes prestate options.

<aconf>

Adds or removes config options.

<set_cookie>

Sets a cookie that will be stored by the user's browser.

<remove_cookie>

Removes a cookie.

<auth-required>

Adds an HTTP auth required header and return code, that will force the user to supply a login name and password.

<expire_time>

Sets the expire-time for the document.

<header>

Adds an HTTP header to the result from page.

<redirect>

Adds an HTTP redirect header and return code to the response from the page.

<return>

Changes the HTTP return code for this page.

<killframe>

Prevents your page from being placed in a frame,