Setting an interval between two quiries

Hi.
I noted a nice feature in Ubuntu forums.
Ubuntu forums doesn't allow you to run two searches, you have to wait for 3 or 15 seconds in order to run the second query.
I'm not a savvy web developer, but how they do this?
Please note that when you submit the form for the second search, the request is sent to the server and a page with an explanation message is displayed, so I don't think JavaScript is used.
Thanks.

Without a better explanation, I'm not sure how to answer.

Here is a small work flow:
Populate search field -> submit the button -> result page
Back button -> Populate search field -> submit the button -> a new page indicating you have to wait for 15 seconds before running your second search

Probably a simple session variable on the server that holds the last time. Before the query is executed the time is looked up from session. If under XXX, it redirects you to the please wait XXX page.

Eric

Have you tried to email their support people and see if they'll just tell you?