/**
* takes target parameter (description|features|screenshots)
* and changes the correspondant css style to a visible state
* and sets the other divs to a css style of display:none
*/
function showDiv(target)
{
	if (target=='d_description')
	{
		$('d_description').show();
		$('d_features','d_screenshots').invoke('hide');
	}
	if (target=='d_features')
	{
		$('d_features').show();
		$('d_description','d_screenshots').invoke('hide');
	}
	if (target=='d_screenshots')
	{
		$('d_screenshots').show();
		$('d_features','d_description').invoke('hide');
	}
}