function getStylesheet(title) {
	// return member of document.styleSheets array having
	// title matching passed parameter.
	// return false if DOM object not available or stylesheet not found
	if (document.styleSheets) {
		var stylesheets = document.styleSheets;
		for ( var i=0; i < stylesheets.length; i++ ) {
			if ( stylesheets[i].title == title ) {
				return stylesheets[i];           
			}
		}	
	}
	return false; 
}

function toggleStylesheet(title) {
	// toggle the 'disabled' property of stylesheet having the passed title
	if ( s = getStylesheet(title) ) {
		s.disabled = !(s.disabled);
	}
}