I have a warning element but i don't know where i have to search

where you can see that plz ?

it’s in openbrowser Activity!
check it once!

ok but where you see that plz ?

in the output panel buddy!
you have to install chrome extension !

do this!
close Chrome Application
go to tools in studio and click on Chrome Extension
then open chrome application and click on Add Extension

i am not using chrome extension but firefox:

okay in property panel change browser type to firefox!

its already done, but it seems has a problem with the extension