Recently We have installed OBIEE 126.96.36.199.0 in one of our windows server environment. After successful installation It was opened Presentation Services with the message "Your Browser is not supported by Oracle Presentation Services"
According to the Latest Oracle Certification Matrix 11gR1 (188.8.131.52+) it supports "Internet Explorer 7.x, Internet Explorer 8.x and .Firefox 3.5+".
If you want to know in detail download certification matrix from here
If we are having the supported version of browsers than we are not getting any issue like this. but if we are not having the same supportable version and want to work with the same version then here is work around which I have resolved in my firefox browser.
The below screen which I got after installation of BI 11g
Before starting the work around, Ensure that you are having Administrator privileges so that I will not block anything.
Open your firefox browser and type "about:config" in the address bar and click 'Enter' button. we will get the screen like below. Click "I'll be careful, I Promise" button from below screen
The next screen will show all the configuration details about the browser. Just right click on the screen and select New-> String
Once we selected String we will get small dialog box which will ask for the new configuration string which we are going to add. Give the name "general.useragent.override" and click OK. Next It will ask for the value of the string. Give the value "Mozilla/5.0 (Windows; Windows NT 6.1; rv:10.0)Gecko/20100101 Firefox/9.0" and click OK.
Now we can see the new configuration agent has been added in the browser configuration details. The main job of this agent is override the existing version to the mentioned value which we have given.
Now 'Refresh' the browser.It will open the Presentation Services.