The article is quite technical, so I’ll try to explain the changes in a less techy manner.
The first major change actually came with IE6 – prior to this release you could append a message to the end of an URL and use various special characters to ‘alter’ the dialog and socially-engineer users to click on the ‘Yes’ button. IE6 brought in sanitisation – it would ‘escape’ these characters so that they had no effect.
But back to SP2. The dialog, instead of defaulting to ‘Yes’, defaults to ‘No’ – so by default your home page won’t be changed.
Microsoft also overhauled the popup code, and one of its changes was to prevent popus from appearing over the top of dialogs. What this meant was that a web page could overlay a popup with no title bar or window controls on top of the dialog to completely change the message. Now that behaviour has been stopped. Popups also must show the title bar and status bar, and cannot be created off screen, effectively making IE’s popup controls more advanced than Firefox’s (shock horror!).
Finally, web pages cannot pop this dialog up automatically. Some pages would present you with the dialog on visiting the page, or upon leaving. Now, the only way this dialog will appear is if you click on a link, giving the user control again.
These are all worthwhile improvements, and it’s evident that Microsoft has actually thought about the user experience and made an effort to improve it. I just wish they’d all come in an earlier release.