Are you using 7.3? In 7.3 the Look & Feel option was removed from Content Pages. If you really need it you can still create a Widget Page and there it should still be available.
May I ask, why you need it?

No, I'm using 6.2 yet  

Any ideia where the old developer remove the button "Look and Feel"

Sounds like you've inherited a system that someone else has locked down.
Ideally, if this was a modification done to the system, it will have been done by some plugin that you could undeploy. In 6.2 you'll find the plugins in Tomcat's webapps directory (provided you use Tomcat) - and some even modify the underlying portal installation as well (namely JSP-hooks)
From a distance it's hard to say where and how this was modified.
On the other hand: Excessive use of Look&Feel is an Antipattern anyway and shouldn't be done. From that point of view, you will end up with a uniform look&feel and always know where to change it: In the theme. ;)