the work for you, while you do more important, difficult things. named oNcliCk set to the alert call. And you'll see at the bottom, there's a link that says URL. JavaScript comment after the alert, then the tag is closed.
jaVasCript:/*-/*`/*\`/*'/*"/*%0D%0A%0d%0a*/(/* */oNcliCk=alert() )//\x3ciframe/