First I look for a site thats not gona take a long time to load. Filling a site with all the bells and whistles just turns me off. Javascript, Flash, Java applets, animations, drop down menus... hey they are nice but one must achive balance. I look for a balance.

Simplicity, easy to use, and functional. Doent mean you cant have your javascripts, but use them in limits without it becomeing an nusance for visitors.

Scroll bar scrollers anoy me, pop up windows realy anoy me. cookies urk me. But hey sometimes you need a cookie, use expirey dates, place meaningfull data in cokies if you must have a cookie. Your alowed 20 I think per domain but seriously why would you need more then two.

Flash animation intros also anoy me, When i type an address or click a link I dont want to visit the man-in-the-middle. I want the site. No click here to enter.

Profesional.