Opera on Thursday released a beta version of Opera Mini 4.1, the company's free Web browser for mobile phones that runs on Java. Most notably, the new release is now signed, which means the phone will not prompt users every time they run the software.

Aside from eliminating the annoying Java security pop-ups, version 4.1 noticeably speeds up Web surfing by up to 50% thanks to improvements to Opera Mini's rendering engine. Accessing sites will be quicker, too, as the browser saves previously entered URLs and auto-completes them for users.

JSR-75 will additionally enable the saving of Web pages for viewing later, when not online. Users can then read a previously downloaded Web page when on the subway, plane or anywhere else they have no cellular signal.

Opera says more than 40 million people have used Opera Mini since the software's debut, although the company will soon face more competition with Apple's iPhone spurring developers like Microsoft and Nokia to beef up their own built-in Web browsers.

With the 4.1 beta release, Opera is soliciting feedback from the community so it can continue to improve the software and stay atop the mobile market. Opera makes money from its free browser by sending Web searches to Google and taking a portion of advertising revenues -- much like Mozilla does with Firefox and Opera with its desktop browser.

"I hope everyone enjoys these new features, but we ask for your candor and feedback as we get ready to make Opera Mini even more relevant to the millions of people who use us and the millions of people who discover Opera Mini every month," says CEO Jon von Tetzchner.