In Oracle Applications professional Users can access professional forms via Appletin web browser.  This Form Applet must run with in Java Virtual Machine (JVM) and Oracle bundles its own JVM as Oracle Jinitiator.  This Jinitiator is available only for Windows Client and for Unix/Linux you have to use Java Plug-In. 
   Till Oracle Apps 11i default JVM was Jinitiator but with Oracle Apps R12 default JVM under which form Applet run is J2SE Plug-In. If you are accessing Oracle Applications (11i/R12), Apps will automatically prompt you to install Jinitiator/J2SE Plug-in (If Jinitiator/J2SE is not installed in client machine) but if you are accessing same Oracle Applications from Linux/Unix it does not prompt to install plug-in and you can’t apps forms from Linux client.

 How to access Oracle Apps 11i/R12 professional forms from Linux Client ?
In you to access forms from Linux client, Three steps are installed (You can skip first if Mozilla is installed on your Linux client) —

1. Install Mozilla Browser
Install JRE on client machine (JRE version to install will depend on Server configuration, 
Identify which version of JRE you need on client machine
— For 11i/R12
: Login to server as application o.s. user (applmgr), set environment variable and run grep plugin $CONTEXT_FILE   (If you get output like 1.5.0_13 you need JRE 1.5.0 patchset 13, if its 1.5.0_10 you need 1.5.0 patchset 10; or for 1.4.2_04 you need 1.4.2 patchset 4 )

3. Use JRE installed above on client machine in Browser (Mozilla) Plugin 

1. Install FireFox Mozilla
–Download Mozilla for Linux from  firefox-
— “gunzip -d firefox-” (You will get unzipped file with name as firefox-
— Extract tar file as “tar -xvf  firefox-”
— This will create directory called “firefox” which is under you will see executable called “firefox“; Use this executable to start FireFox on Linux machine.

2. Install JRE on client machine
–Download JRE  5.0 Update 10 (change this as per your server plugin version shown above; I am on 12.0.0 hence 1_5.0.10)   for Linux from  “jre-1_5_0_10-linux-i586-rpm.bin
–“chmod 755 jre-1_5_0_10-linux-i586-rpm.bin”
–./jre-1_5_0_10-linux-i586-rpm.bin  (You will be asked to accept license agreement , click enter and when prompted to accept license enter Yes)
–This will install jre 1.5.10 in linux machine under /usr/java  and plugin is installed under /usr/java/jre1.5.0_10/plugin/i386/ns7/

Configure JRE Plug-in in browser
–Go to Mozilla FireFox plug-in directory which is $location_where_you_unziped_firefox_directory/plugins and create soft link like
–ln -s /usr/java/jre1.5.0_10/plugin/i386/ns7/ ./