var zoom_factor = 1;

var ZOOM_MIN 		= 1;
var ZOOM_MAX		= 2.5;

/**
 * Writes the zoom with the specified factor.
 */
/*void*/ function zoom(factor)
{
	if (!factor)
		return;

	if (document.body.style.zoom != undefined /*document.all && document.getElementById*/)
	{
		// save zoom factor
		var newZoom = zoom_factor;

		if (factor < 0)
		{
			newZoom /= Math.abs(factor);
		}
		else
		{
			newZoom *= factor;
		}

		// assign new zoom if it is valid
		if (newZoom >= ZOOM_MIN && newZoom <= ZOOM_MAX)
		{
			document.body.style.zoom = zoom_factor = newZoom;
		}
	}
}