@DavidR: when I can use Firefox or IE or Safari to see all web-site in their view why should I hurt myself to use Opera?!
we cannot ignore MANY website because they are not working with Opera (Or WC3)... instead, I can Change ONE BROWSER and see ALL WEBSITE in their best view 
I have tried Opera several times and I simply don't like the interface (I much prefer firefox), all I'm pointing out that this problem isn't of Opera's making. If as you say you also used it for browsing via a java mobile then you are once again adding another complication as browsing via a mobile would generally require that the site has wap pages.
I strongly doubt that the many web sites can't be displayed in Opera or there would be huge media publicity about this and we just aren't seeing it.
If a web designer isn't conforming to wc3 standards then they are doing a disservice to the site owner, as it restricts access to his site that he paid good money for the design, etc.
I designed a number of web sites (many years ago now) and used a wc3 validator against the code to get rid of the most obvious issues. At that time I had a copy of the most common browsers (including Opera) and view all the pages with the different browsers until they all displayed the page the same, which wasn't easy but most certainly possible.
So me I never blame a browser which is standards compliant for the failure of the designer to comply with standards, that is after all why they are called standards, to ensure it works for all browsers. The obvious exception being those with activeX and they are becoming fewer as I don't often bump into those with firefox and that generally isn't a deal breaker as only the activeX element won't work, which for me is just fine as activeX can be a malware magnet.
