Orkut is a social networking website popular in India and Brazil, in-fact I found many of my school friends whom I wasn’t in touch in Orkut. Orkut provides users with themes, however the official themes provided are limited in number and there are lots of Free Orkut Themes you can easily use to customize your Orkut profile.
If you are a Orkut user and are looking to spice up your profile, here are some simple steps that will teach you how to apply / install or change custom themes in your Orkut profile.
The Orkut themes can only be applied and view in Firefox, so you may want to download Firefox before you follow the rest of the steps.
Step 1: In order to apply custom themes to your Orkut profile, you will need to download and install a Firefox add-on called Greasemonkey.
Step 2: Choose one of the themes from this huge list of Free Orkut Themes.
Step 3: Install the userscript that is required for the theme and enjoy the custom theme for your Orkut profile 
If you are not using Firefox, there is a option to run Greasemonkey scripts on other browsers such as Internet Explorer, Opera and Safari, do read the tutorial on Techie Buzz to run Greasemonkey scripts in Internet Explorer, Safari and Opera browsers.
I have installed the firefox and added the greasmonkey in that and installed the theme in that but i am unable to view then new theme which i have installed can u suggest to apply that