var browsername = navigator.appName;

var browserversion = navigator.appVersion;

//if (browsername = 'Microsoft Internet Explorer')

browserversion = browserversion.search(/MSIE 6.0/i);

if (browsername = 'Microsoft Internet Explorer' && browserversion > 0) 

	{ alert('Internet Explorer 6 detected. Please use Internet Explorer 7 or above for best viewing experience.')  }