Get your /h5bp/-like HTML classnames for IE versions dynamically. Useful if you don't have control of the raw markup as spat out by the server.

ieVersion.js

// Optain classnames representing the IE rendering engine:
// Makes version-targetted CSS much cleaner
var sIEclass = (function determineIEversion(){
	// A DOM element to run the test on
	var oTest     = document.createElement('test');
	// A table matching tested versions to representative class string
	var hVersions = {
		"6" : "ie ltie10 ltie9 ltie8 ltie7 ie6",
		"7" : "ie ltie10 ltie9 ltie8 ie7",
		"8" : "ie ltie10 ltie9 ie8",
		"9" : "ie ltie10 ie9"
	};
	// A conditional comment with `#` as a placeholder for the IE version
	var sMarkup   = '<!--[if IE #]>#<![endif]-->';
	// Store any matched versions here
	var aMatch;

	// Loop through test candidate versions
	for(var sVersion in hVersions){
		if(hVersions.hasOwnProperty(sVersion)){
			// Append a conditional comment for each, targetted to that version,
			// containing that version number as a text node
			oTest.innerHTML = oTest.innerHTML + sMarkup.replace(/#/g, sVersion);
		}
	}

	// Non-IE && IE10+ browsers will read the contents as several comments;
	// Old IEs will see just their respective version number
	aMatch = oTest.innerHTML.match(/^\d$/);

	if(aMatch){
		// Return the class string corresponding to the retrieved version number
		return hVersions[aMatch[0]];
	}
}());

document.lastChild.className += ' ' + sIEclass;

ieVersion.mini.js

// False for IE10 and above, integer otherwise
var ieVersion = (function getIEVersion(){
	var test     = document.createElement('x');
	var comment  = '<!--[if IE #]>#<![endif]-->';
	var versions = 10;

	while(--versions){
		test.innerHTML += comment.replace(/#/g, versions);
	}

	return ~~test.innerHTML || false;
}());