Open URL just via clicking on it on the page. (without post and Session). How they do it?

I'm wondering, how some pages do that. I can click on the link, it opens; but when i copy the url and paste it to the address bar, it doesn't open...I checked if some Post variables will be sent, but they won't actually..

like this example..If you click on this, it won't be opened. http://www.zvg-portal.de/index.php?button=showAnhang&land_abk=he&file_id=35957&zvg_id=19697

but if you go to the page and click on the document, you will be able to open it..

In this example it isn't using POST variables, it is using the URL querystring components. You can use these in PHP using the $_GET sytax.

This site probably works by having conditional output / functionality based on the setting / getting of these querystring components.

Maybe the server checks for HTTP_REFERER . That means the link will only open from a particular page. http://en.wikipedia.org/wiki/HTTP_referrer . You can manipulate this by eithe using something like CURL or maybe a browser plugin.