Hide the window decorations for firefox and opera

I’ve found a way to hide window decorations in metacity for Opera and Firefox:

<ul>
	- install devilspie
	- create files opera.ds and firefox.ds in your ~/.devilspie directory with the following content:
</ul>

(if (is (application_name) "Firefox") and (contains (window_name) "Mozilla Firefox")
             (begin
                (undecorate)
             )
)

(if (is (application_name) "Opera") and (is (window_name) "Opera")
             (begin
                (undecorate)
             )
)

<ul>
	- run devilspie and check if everything works
	- place devilspie in autostart
</ul>