These are CSS properties, not HTML elements. There is no need to sniff; you just provide multiple properties. p.wibble { -moz-blink: slowly; -webkit-blink: 10%

These are CSS properties, not HTML elements. There is no need to sniff; you just provide multiple properties. p.wibble { -moz-blink: slowly; -webkit-blink: 10%; -ie9-blink: "Microsoft.XML.Autocompositor(alpha=99,blinkrate=14692,emulate-old-ie-versions=false,true,true,false)#ie9" } or whatever. (In practice everyone who provides these properties does so in a very similar manner, so it's easier than the above pseudosnippet suggests.)