function gettingIt() {
  var elements = new Array();

  for (var i = 0; i < arguments.length; i++) {
    var element = arguments[i];
    if (typeof element == 'string')
      element = document.getElementById(element);

    if (arguments.length == 1) 
      return element;

    elements.push(element);
  }

  return elements;
}

Element.setBackgroundPosition = function(element, position) {
    element = gettingIt(element);
    element.style['backgroundPosition'] = position;
    return element;
  };
Element.show = function(element) {
    element = gettingIt(element);
    element.style['display'] = 'block';
    return element;
  };
Element.hide = function(element) {
    element = gettingIt(element);
    element.style['display'] = 'none';
    return element;
  };

function overview_open () {
	// show selected tab & show selected content
	if(document.getElementById('overview_content')) {
		Element.setBackgroundPosition('nav_overview', '0px 0px');
		Element.show('overview_content');
	}
	if(document.getElementById('tech_content')) {
		Element.setBackgroundPosition('nav_tech', '0px -58px');
		Element.hide('tech_content');
	}
	if(document.getElementById('features_content')) {
		Element.setBackgroundPosition('nav_features', '0px -58px');
		Element.hide('features_content');
	}
	if(document.getElementById('reviews_content')) {
		Element.setBackgroundPosition('nav_reviews', '0px -58px');
		Element.hide('reviews_content');
	}
}

function tech_open () {
	// show selected tab & show selected content
	if(document.getElementById('overview_content')) {
		Element.setBackgroundPosition('nav_overview', '0px -58px');
		Element.hide('overview_content');
	}
	if(document.getElementById('tech_content')) {
		Element.setBackgroundPosition('nav_tech', '0px 0px');
		Element.show('tech_content');
	}
	if(document.getElementById('features_content')) {
		Element.setBackgroundPosition('nav_features', '0px -58px');
		Element.hide('features_content');
	}
	if(document.getElementById('reviews_content')) {
		Element.setBackgroundPosition('nav_reviews', '0px -58px');
		Element.hide('reviews_content');
	}
}

function features_open () {
	// show selected tab & show selected content
	if(document.getElementById('overview_content')) {
		Element.setBackgroundPosition('nav_overview', '0px -58px');
		Element.hide('overview_content');
	}
	if(document.getElementById('tech_content')) {
		Element.setBackgroundPosition('nav_tech', '0px -58px');
		Element.hide('tech_content');
	}
	if(document.getElementById('features_content')) {
		Element.setBackgroundPosition('nav_features', '0px 0px');
		Element.show('features_content');
	}
	if(document.getElementById('reviews_content')) {
		Element.setBackgroundPosition('nav_reviews', '0px -58px');
		Element.hide('reviews_content');
	}
}

function reviews_open () {
	// show selected tab & show selected content
	if(document.getElementById('overview_content')) {
		Element.setBackgroundPosition('nav_overview', '0px -58px');
		Element.hide('overview_content');
	}
	if(document.getElementById('tech_content')) {
		Element.setBackgroundPosition('nav_tech', '0px -58px');
		Element.hide('tech_content');
	}
	if(document.getElementById('features_content')) {
		Element.setBackgroundPosition('nav_features', '0px -58px');
		Element.hide('features_content');
	}
	if(document.getElementById('reviews_content')) {
		Element.setBackgroundPosition('nav_reviews', '0px 0px');
		Element.show('reviews_content');
	}
}