var aActiveX = ['MSXML6.DomDocument', 'MSXML3.DomDocument', 'MSXML2.DomDocument', 'MSXML.DomDocument', 'Microsoft.XmlDom'];
var oDOM;
if (navigator.appName == 'Microsoft Internet Explorer') {
                for (var n = 0; n < aActiveX.length; n++) {
                                try {
                                                oDOM = new ActiveXObject(aActiveX[n])
                                } catch(oException) {}
                }
} else {
                if (document.implementation && document.implementation.createDocument) {
                                oDOM = document.implementation.createDocument('', '', null)
                }
}
var oDem = oDOM.createElement('dem');


alert('getElementsByTagName' in oDem);
try {
                alert(oDem.getElementsByTagName)
} catch(e) {
                alert(e)
}