function CheckForm() {
    if (document.getElementById('sizabil').value=="select"){
      alert('Vyber si velikost z nabídky nad tlacítkem "Pridat do kosíku"!');
      return false;
    }else{
      return true;
    }
  
}        


function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      if (oldonload) {
        oldonload();
      }
      func();
    }
  }
}