One of the nicest features in the upcoming Opera 9.5 is that the “save this password” prompt doesn’t hold back the website from loading. This gives the site an opportunity to log you in before saving would could potentially be an incorrect username or password.
The latest Firefox 3 nightlies also have a similar feature, but I believe it is implemented a little better than Opera’s. Firefox doesn’t use a popup dialog box anymore to ask the user to save a password, instead it shows a slim bar along the top of the site (pictured above). It’s unobtrusive, small, and doesn’t interrupt the browsing experience of the user.
Unfortunately no browser has figured out a way to determine whether the login was successful, and if the login wasn’t correct prevent the password-saving option from even appearing. However, this is a good enough alternative for me and I think most users will truly appreciate it.
One other thing that Mozilla added was a bar that appears when trying to install an extension from an untrusted site. Prior to this you had to whitelist a site before you could install an extension from it, but now you can temporarily allow it: