I use a host file for malware and some ad blocking. The result of a webpage that uses iframes directed at a domain that i have forbidden is Opera's error message. "This webpage is not available". The irony is that the error message [or messages as sometimes there are multiple iframes on a page] is more unattractive than the content of the iframe. Especially for dark pages where the background is often black. It sticks out too much. Chrome's 404 page is a bit more discreet being just a gray with icon in the center.
Two points i'd like to make.
I still prefer using the host file as opposed to the more popular in browser extensions due to stability / quickness and providing a whole system blockout. As I use multiple browsers.
For sites that I do visit often I do use the extension 'Stylish' and create rules to remove page elements I don't like. Which can be 'error messaged' iframes.
But what i'm looking is a way to change Opera's Error message for a 404 Error. For random browsing or web surfing of sites you have not previously been to and improving the user experience without multiple iframe error messages. If it could be made to be like chrome's that would be fine. But preferably Either a way to make it 'display : none' or allow a user created html page would be great.
I pose this thought to the community and well as the Opera dev. team. I'm not sure a opera / chrome extension will have the permissions to change the 404 page. Cross site scripting rules generally means the main page can't know anything about the iframe's content.
Actually if you look on stylish's page of posted styles for websites you would find that people actually can apply a style to Firefox's 404 error page. Not compatible with chrome / opera. I believe it has to do with the url of the 404 message. Firefox makes it about:config something.. which you can set as a target domain to style.. While chrome / Opera keeps the original url for the iframe, whether it is a 404 page or not.
If anyone knows of a way to hide or change this message please let me know.