Although dangerous trick such as [`behavior: url('some.htc')`](http://msdn.microsoft.com/en-us/library/ie/hh801216(v=vs.85).aspx) aren't available in modern browsers by default, if you are using the [`X-UA-Compatible`](http://www.modern.ie/en-us/performance/how-to-use-x-ua-compatible) header or meta tag to force Microsoft Internet Explorer in a different render mode, or if you are ommitting the document type declaration, Internet Explorer will use the behavior of older versions where such things are available.