Can i bring a webpage (node) up/down using irules?

I agree with Cory (of course :-) ) - you don't want to use iRules for this.

You could make it easier for the admin by having him (or her) rename the file instead of creating/deleting the file. For a more elegant solution you could have the web resource return a specific HTTP response code (e.g. 200, 500). Even more elegant would be to do this in a CMS or via an admin app.

Or you could just have the admin disable the instance on the server (e.g. Apache, IIS).