Hallvord who works for Opera has discovered and posted a fix to allow Opera to work with dsl.sbc.yahoo.com.

Yahoo has a long history of blocking Opera for no reason. One might even mistake them for MSN.

Did Opera ever not work correctly at Yahoo? Not that anyone is aware of. And if so, it has been a long time now. Back in December 2003 it was known that Opera could work with Yahoo if you just managed to fool Yahoo into thinking that you were not using Opera.

Shame on Yahoo for being against the freedom to choose your own browser.

Fortunately now that we have User JavaScript, we can solve many of these problems.

Personally, I don’t know anything about JavaScript except that it causes problems a lot of the time (popups and other annoyances) but is often required by brain-dead sites which care more about control than users. (Use JavaScript to add functionality, not as a requirement.) I don’t plan to learn much JavaScript. But the cool thing is that Opera lets me fix things by using tips from other smart people.

In addition to Hallvord’s fix, someone also suggested this:

 if (document.domain.match(/^(dsl\.)?sbc\.yahoo\.com$/)) {
   window.operaOld = window.opera;
   window.opera = null;
 }

which works for me.

Update: Also: see another important consideration below in the comments section, including a link to another, possibly better, solution.