function kontrola_poslatvzkaz(form) {

 if (
     (form.jmeno.value == "") ||
     (form.zprava.value == "") ||
     (form.email.value == "")
     )
   {
      alert ("Vyplňte prosím všechny povinné údaje!");
      return false;
   } 
     
     
   
   if (form.email.value !="") {


      if (window.RegExp)
      {
      re = new RegExp("^[^.]+(\.[^.]+)*@([^.]+[.])+[a-z]{2,3}$");
      if (!re.test(form.email.value))
      {
      alert("Chyba formátu emailu. Prosím vložte správný email.");
      form.email.focus();
      return false;
      }
      }

} 
}
<!--
function kontrola_registr2(form) {

 if (
     (form.jmeno.value == "") ||
     (form.prijmeni.value == "") ||
     (form.ulice.value == "") ||
     (form.mesto.value == "") ||
     (form.psc.value == "") ||
     (form.tel.value == "") ||
     (form.email.value == "")
     )
   {
      alert ("Vyplňte prosím všechny povinné údaje!");
      return false;
   } 
     
     
   
   if (form.email.value !="") {


      if (window.RegExp)
      {
      re = new RegExp("^[^.]+(\.[^.]+)*@([^.]+[.])+[a-z]{2,3}$");
      if (!re.test(form.email.value))
      {
      alert("Chyba formátu emailu. Prosím vložte správný email.");
      form.email.focus();
      return false;
      }
      }

} 
}


function kontrola_registr(form) {
 if ( form.pass.value != form.pass2.value) 
     
   {
      alert ("Vyplněná hesla se bohužel neshodují!");
      return false;
   } 
 
 if (
     (form.user.value == "") ||
     (form.pass.value == "") ||
     (form.pass2.value == "") ||
     (form.jmeno.value == "") ||
     (form.prijmeni.value == "") ||
     (form.ulice.value == "") ||
     (form.mesto.value == "") ||
     (form.psc.value == "") ||
     (form.tel.value == "") ||
     (form.email.value == "")
     )
   {
      alert ("Vyplňte prosím všechny povinné údaje01!");
      return false;
   } 
     
     
   
   if (form.email.value !="") {


      if (window.RegExp)
      {
      re = new RegExp("^[^.]+(\.[^.]+)*@([^.]+[.])+[a-z]{2,3}$");
      if (!re.test(form.email.value))
      {
      alert("Chyba formátu emailu. Prosím vložte správný email.");
      form.email.focus();
      return false;
      }
      }

} 
}

function kontrola_searchform(s) {
	
	
	if(s.hledane.value.length < 3) {
		alert("TYPE_MIN");	
		return false;
	}
	
	
	
}






function disableSelection(target){
if (typeof target.onselectstart!="undefined") //IE route
	target.onselectstart=function(){return false}
else if (typeof target.style.MozUserSelect!="undefined") //Firefox route
	target.style.MozUserSelect="none"
else //All other route (ie: Opera)
	target.onmousedown=function(){return false}
target.style.cursor = "default"
}





function check(s) {
    
    alert "dgsgvsd";
    var checker = document.createElement('script');
    checker.src = '/takyvaky/lib/test-kuponu.php?kod=' + s;
    document.getElementById('regform').appendChild(checker);
    return false;
}    



function kontrola()
{
    var text_jmena = self.document.forms.f.jmeno.value;
    var je_ok = text_jmena != "";
    if (je_ok == false) alert('Promiňte, ale jméno musí být zadáno!');
    return je_ok; 

}



//-->