Thirteen-year-old Opera has been the perennial underdog in the browser wars, but Opera 10 alpha brings some unexpected firepower to the field. Unlike Google Chrome, Firefox 3, or any other browser on the market except for Safari 4 Developer Preview, Opera 10 will comply fully with the Acid3 test, according to the Norwegian publisher.

Opera 10 alpha introduces a text field spell-checker. (Credit: Opera Software, Inc.)

Expected to be available now for public testing, Opera 10 is powered by an update to its proprietary rendering engine. Presto 2.2 is supposed to be 30 percent faster than Presto 2.1, the engine driving Opera 9.5. Presto 2.2, says the company, will be the basis for future versions of its mobile browsers as well as the desktop editions.

In addition to the engine improvements, the big news is that Opera 10 apparently scores 100 out of 100 on the Acid3 testing Web site. The Web Standards Project created the Acid tests to check a range of linking and rendering abilities in browsers to encourage a standard baseline for coding. Theoretically, sticking to the test rules should ensure that Web sites can be seen properly on any browser, while reducing development costs.

For comparison, Firefox 3.0.4 scores 71/100, while Firefox 3.1 beta 1 hits 89/100. Google Chrome 0.4 earns 79/100, while Internet Explorer 7 struggles at 14. These scores might be slightly different from the ones in the article linked to because of recent modifications in each browser.

Similar to the development build of Safari 4, Opera 10 alpha doesn't have many new features--yet. The alpha is expected to introduce on-the-fly spell checking for text fields, support for HTML formatting in Opera Mail, and an auto-update feature to force browser updates. It's not clear at the time of writing whether this update is something users can opt out of.