The IE8 proprietary property (and vendor extension) lowdown

Whilst there was me thinking the IE team were going to be sticking rigidly to 2.1 compliance and nothing else, it was announced on the IE Blog that a number of proprietary and level 3 properties are going to be implemented yet again on an experimental basis (using the -ms- prefix).

Most of the level 3 properties deal specifically with text layout (layout-grid, line-grid, line-break, word-wrap), but they’ve also prefixed some non text layout-specific properties including background-position-x & background-position-y and overflow-x & overflow-y.

One thing I was surprised to see was the amount of proprietary properties that they are continuing to support; in case you’re not already familiar with the functionality of these properties, I’d thought I’d come up with a brief intro for each of the most interesting properties (full property list):-

• -ms-interpolation-mode – Introduced in IE7, this property deals with smooth image scaling; this gives the author the ability to de-scale large images using CSS, without losing definition. The two keyword values that can be used are nearest-neighbor (using nearest neighbor interpolation mode) and bicubic (using high-quality bicubic interpolation mode). MSDN page
• -ms-filter – Probably the most used property on the list as it is currently the only way to emulate opacity in versions of IE. NOTE: MS have recognised that the former syntax used to emulate opacity was illegal, so they have no re-written the value.
• -ms-accelerator – As far as I’m aware, this is a brand new extension for IE8 and there is currently no specification from MS on it’s function.
• -ms-behaviour – This property allows a script to be attached to the element to which it is applied; the script that is specified in the property is saved as an HTC file (HTML Component). I’d hazard a guess that the most common purpose of this property is getting semi-transparency in PNGs working in IE5+. MSDN page
• -ms-scrollbar-* – This set of properties has been with us since IE5 and the property name is pretty self-explanitory; they’re used to control the colour of the browser window scrollbars.
• -ms-text-underline-position – Supported since IE6, this property sets the position of the underline that is set through the text-decoration property.
• -ms-zoom – sets the maginfication scale of an element.