I've been impressed this past year with all the excellent things I hear about the Opera web browser. I'm a die-hard Firefox browser user myself, but I nevertheless appreciate the work being done on other web browsers.

So imagine my chagrin when, after installing Opera verison 9 on my computer, I discover that I can't log on to a family web site that I and members of my family use regularly to communicate with one another. Firefox works just fine on the site, but Opera, which has superior CSS rendering, is smaller, and is faster than Firefox, chokes.

It was totally a surprise.

To diagnose the problem, I had to whip out the Ethereal [EDIT: Since originally published, Ethereal was renamed Wireshark] network sniffer/analyzer and watch the raw HTTP traffic between Opera and the web server. I was further surprised to see that the problem was Opera's fault, and not the web site's problem (which at first I had suspected).

It seems that Opera has a problem consistently sending cookies back to a web site that sets them. Further, it seems that this only happens when Opera has the "Accept only cookies from the site I visit" configuration option set. (And indeed, this is how I had my Opera browser configured, because I prefer to only accept cookies directly from web sites I visit.)

I've created a pair of browser bug demonstration pages. Check them out here: http://www.adg.us/operabug.html

A little googling around, and I see that Opera 9 has had some odd cookie problems for quite a while, even during beta. Why the excellent Opera programmers (who have a browser that passes the stressful Acid 2 Test while Firefox still has troubles) haven't fixed this yet astonishes me.

So please, if you're an Opera programmer, please, please, PLEASE fix this bug! (Thanks in advance!)

Update: April 2007 - Version 9.10 of Opera under Mac OS X and also under Windows XP do not have this bug. Thanks, Opera programmers!