function switchTab(obj) {
            var suffix = '_content';
            var tabPrefix = 'tab';
            var objTab = null;
            var objCopy = null;
            for(i=0;i<=3;i++) {
                objCopy = document.getElementById(tabPrefix+i);
                objTab = document.getElementById(tabPrefix+i+suffix);
                if(objCopy != null && objTab != null) {
                    if (obj.id != tabPrefix+i) {
                        objCopy.className = 'hiddenTab';
                        objTab.className = 'hiddenT';
                    } else {
                        obj.className = 'visibleTab';
                        objTab.className = 'visibleT';
                    }
                }
            }
        }