To install the latest version of opera browser on Ubuntu 11.04 Desktop (Natty Narwhal) follow the instructions below :
1- Open Firefox with Opera website www.opera.com
then click on Download Opera 11.50 For linux .
2-Save the file to your hard drive .
3-Open the downloaded file , it will open ubuntu Software center with Opera , click on installti install it.
4- Have fun with Opera browser.