function tabs(goal) {
	
	resetTabs();
		
	// set non active elements
	window.document.getElementById(goal).style.display = "block";
	if(goal=='catalog') {
		swapStyle(window.document.getElementById('z1'),'on');			
	} else if (goal=='most-visited') {
		swapStyle(window.document.getElementById('z2'),'on');
	} else if (goal=='interesting-pages') {
		swapStyle(window.document.getElementById('z3'),'on');
	}
}

function swapStyle(target,set) {
  // set swap style for active / non active elements
	if (set == "on") {target.className = 'active';}
	else if (set == "off") {target.className ='normal';}
}

function resetTabs() {
	// reset all tabs
	window.document.getElementById('catalog').style.display = "none";
	window.document.getElementById('most-visited').style.display = "none";
	window.document.getElementById('interesting-pages').style.display = "none";
	swapStyle(window.document.getElementById('z1'),'off');
	swapStyle(window.document.getElementById('z2'),'off');
	swapStyle(window.document.getElementById('z3'),'off');
}

function examples(goal) {
	
	resetExamples();
		
	// set non active elements
	window.document.getElementById(goal).style.display = "block";
	if(goal=='galerie') {
		swapStyle(window.document.getElementById('z1'),'on');			
	} else if (goal=='unikatni') {
		swapStyle(window.document.getElementById('z2'),'on');
	} else if (goal=='administrace') {
		swapStyle(window.document.getElementById('z3'),'on');
	}
}
function resetExamples() {
	// reset all tabs
	window.document.getElementById('galerie').style.display = "none";
	window.document.getElementById('unikatni').style.display = "none";
	window.document.getElementById('administrace').style.display = "none";
	swapStyle(window.document.getElementById('z1'),'off');
	swapStyle(window.document.getElementById('z2'),'off');
	swapStyle(window.document.getElementById('z3'),'off');
}