I am assuming this is windows.
For Firefox you can go to about:addons and on the left click on Plugins to make sure it is there, you can also see if it is Disabled and if so Enable it
For Internet Explorer you can go to Tools -> Manage Addons - On the left Tools and Extensions at the middle, select Currently Loaded Addons, you should see Java under the Oracle heading.
For Chrome go to chrome://plugins/ and see if it is listed.
Also one thing to look at is are you using the 64-bit version of the web browsers and if so you would need the 64-bit java for it and not the 32 bit
Another thing that Webbrowser are doing is possibly blocking the plugin from running, I know in Firefox and Chrome I see a warning asking if I want to run the plug in