The Microsoft Internet Explorer in aspects of web standards, versions, its behavior and also of crossbrowser compatibility has always been a challenge for webdevelopers and webdesigners.
Referring to this former evolution, it is not further surprising that HTML5 and CSS3 bring in a whole batch of new challanges.
Especially in the matter of fact, that these technologies are in a relatively early stage of development that is additionally influenced by competing standard definitions between the W3C and the wider WHATWG standard.
(The WHATWG represents an alliance of different brwowser companies and experts that are partially Members of the W3C workingroup, too)
In this article I will introduce some tools that might be helpful to you, especially in the intention of avoiding IEs "conditional comments" by the reason of their insufficient speed performance and using CSS3 in IE versions below IE Version 9.0.
The following tools, "CCS3Pie" and "Modernizr" will enable you to implement some of the most requested CSS3 Features into IE6 and higer.
The "Modernizr" Script, allows you to check wich browser and Browserversion is requesting your actual Page, wich different HTML5 and CSS3 Features are supported by this browser and browser version, and finally enables you, to deploy appropriate CSS Code for every given case you want. (And last but not least offers a fallback for Browsers with JavaScript disabled. At least an average of 1%)
So lets have a look on these tools...