Not displaying in IE7

Lectora 2005 SP4a shows correctly with IE6 and Firefox but in IE7 comes up with error "InnerWidth" is undefined.The relevant code may be the following:function menuObj(obj, par, nst, p) { page = new Object(); page.width = (is.ns6 || is.ns6x || is.ns4 || is.moz) ? innerWidth : document.body.clientWidth; page.height = (is.ns6 || is.ns6x || is.ns4 || is.moz) ? innerHeight : document.body.clientHeight;Is there a workaround for this?ThanksMarc