Just a handful of weeks ago, the developers of Opera 10.5 were calling their "pre-alpha" build dangerous if used to run a nuclear reactor facility. Over the weekend, in what appears to have been a round-the-clock effort to compress a few months' work into a few days' time, Opera Software ticked through four release candidates of its latest Windows-based Web browser.

document.write('<scr'+'ipt language="javascript" src="http://ad.doubleclick.net/adj/ns.betanews/articles;net=ns;u=,ns-68247048_1268303824,1177079950047dd,it_general_opensource,;;kw=;tile=2;ord1=597871;sz=300x250ord=6876554089766220;ppos=ATF;contx=it_general_opensource;btg=?"></scr'+'ipt>'); CollectiveMedia.createAndAttachAd("ns-68247048_1268303824","http://ad.doubleclick.net/adj/ns.betanews/articles;net=ns;u=,ns-68247048_1268303824,1177079950047dd,it_general_opensource,;;kw=;tile=2;ord1=597871;sz=300x250ord=6876554089766220;ppos=ATF;contx=it_general_opensource;btg=?","300","250ord=6876554089766220",false); The reason, of course, is Microsoft's rollout of its browser choice screen for European users of older versions of Internet Explorer. Some users reported seeing the screen for the first time over the weekend, though the full-scale rollout began in earnest today.