If you want to use the OBIEE 11.1.1.5.0 with Firefox 10+ there is one work around. if you want you can try it(i have implemented the same and it works like a charm)
1. type "about:config" into an address bar
2. right click anywhere and choose New / String
3. name it "general.useragent.override"
4. put the value "Mozilla/5.0 (Windows; Windows NT 6.1; rv:10.0)Gecko/20100101 Firefox/9.0"
5. refresh OBIEE login screen
thats it you are good now to use OBIEE 11g with FF.
1. type "about:config" into an address bar
2. right click anywhere and choose New / String
3. name it "general.useragent.override"
4. put the value "Mozilla/5.0 (Windows; Windows NT 6.1; rv:10.0)Gecko/20100101 Firefox/9.0"
5. refresh OBIEE login screen
thats it you are good now to use OBIEE 11g with FF.
