Of course, the humor here lies in the fact that IE has had dynamic CSS calculations since IE 5, but is now in the process of removing them – just as they are being standardized in other browsers.
For example [1]:
<div style="left:expression(document.body.clientWidth/2-oDiv.offsetWidth/2);">Content</div>
These expressions (or "dynamic properties") essentially evaluated JScript embedded inside a stylesheet and provided some handy hacks to get around otherwise-painful bugs. This included simple math calculations as described in the Mozilla post, but also more complex transformations such as varying the style of an element based on the current day (or other JS-retrievable information).
Funny to see Mozilla phasing this in just as Microsoft phases something similar out [2].
The problem with Microsoft's implementation is that it allowed any Javascript to be executed -- so CSS became a vector for XSS attacks (one of the early MySpace worms was based on this feature). This implementation only allows very basic math, and is so is inherently a lot safer.
Completely agree - Mozilla's scaled-back implementation, which appears to be closer in line with the standards track - is much safer and marks a better approach anyway (several at MS have been openly recommending against using dynamic attributes for some time now).
It's moves like this among vendors that force us to think about that line between "experimentation and innovation" vs. implementing "proprietary features."
As NathanKP mentioned below, we'd all do well to push vendors to come back together toward standard implementations across all popular browsers. Here's hoping.
For example [1]: <div style="left:expression(document.body.clientWidth/2-oDiv.offsetWidth/2);">Content</div>
These expressions (or "dynamic properties") essentially evaluated JScript embedded inside a stylesheet and provided some handy hacks to get around otherwise-painful bugs. This included simple math calculations as described in the Mozilla post, but also more complex transformations such as varying the style of an element based on the current day (or other JS-retrievable information).
Funny to see Mozilla phasing this in just as Microsoft phases something similar out [2].
[1] http://blogs.msdn.com/b/ie/archive/2008/10/16/ending-express...
[2] http://msdn.microsoft.com/en-us/library/ms537634(VS.85).aspx...