function strlen (string) {
    // http://kevin.vanzonneveld.net
    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   improved by: Sakimori
    // +      input by: Kirk Strobeck
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   bugfixed by: Onno Marsman
    // +    revised by: Brett Zamir (http://brett-zamir.me)
    // %        note 1: May look like overkill, but in order to be truly faithful to handling all Unicode
    // %        note 1: characters and to this function in PHP which does not count the number of bytes
    // %        note 1: but counts the number of characters, something like this is really necessary.
    // *     example 1: strlen('Kevin van Zonneveld');
    // *     returns 1: 19
    // *     example 2: strlen('A\ud87e\udc04Z');
    // *     returns 2: 3
 
    var str = string+'';
    var i = 0, chr = '', lgth = 0;
 
    var getWholeChar = function (str, i) {
        var code = str.charCodeAt(i);
        var next = '', prev = '';
        if (0xD800 <= code && code <= 0xDBFF) { // High surrogate (could change last hex to 0xDB7F to treat high private surrogates as single characters)
            if (str.length <= (i+1))  {
                throw 'High surrogate without following low surrogate';
            }
            next = str.charCodeAt(i+1);
            if (0xDC00 > next || next > 0xDFFF) {
                throw 'High surrogate without following low surrogate';
            }
            return str.charAt(i)+str.charAt(i+1);
        } else if (0xDC00 <= code && code <= 0xDFFF) { // Low surrogate
            if (i === 0) {
                throw 'Low surrogate without preceding high surrogate';
            }
            prev = str.charCodeAt(i-1);
            if (0xD800 > prev || prev > 0xDBFF) { //(could change last hex to 0xDB7F to treat high private surrogates as single characters)
                throw 'Low surrogate without preceding high surrogate';
            }
            return false; // We can pass over low surrogates now as the second component in a pair which we have already processed
        }
        return str.charAt(i);
    };
 
    for (i=0, lgth=0; i < str.length; i++) {
        if ((chr = getWholeChar(str, i)) === false) {
            continue;
        } // Adapt this line at the top of any loop, passing in the whole string and the current iteration and returning a variable to represent the individual character; purpose is to treat the first part of a surrogate pair as the whole character and then ignore the second part
        lgth++;
    }
    return lgth;
}


var povinne_barva = "#FF3300";
var colour = "#FFFFFF";

function validate(formular)
{
   
    if (formular.username.value=="")
    {
        alert("Vyplňte prosím Vaše uživatelské jméno");
        formular.username.focus();
        formular.username.style.backgroundColor=povinne_barva;
        formular.username.style.color = colour;
        return false;
    }
    else if (formular.pass1.value=="")
    {
        alert("Vyplňte heslo");
        formular.pass1.focus();
        formular.pass1.style.backgroundColor=povinne_barva;
        return false;
    }
    else if (strlen(formular.pass1.value) < 5)
    {
        alert("Heslo musí mít více jak 5 znaků");
        formular.pass1.focus();
        formular.pass1.style.backgroundColor=povinne_barva;
        return false;
    }    
    else if (formular.pass2.value=="")
    {
        alert("Vyplňte heslo podruhé");
        formular.pass2.focus();
        formular.pass2.style.backgroundColor=povinne_barva;
        return false;
    }  
    else if (formular.pass1.value != formular.pass2.value)
    {
        alert("Hesla si neodpovídají, zadejte je prosím znovu.");
        formular.pass1.focus();
        formular.pass1.style.backgroundColor=povinne_barva;
        formular.pass2.focus();
        formular.pass2.style.backgroundColor=povinne_barva;
        return false;
    }  
    else if (formular.firstname.value == "")
    {
        alert("Vyplňte Vaše jméno.");
        formular.firstname.focus();
        formular.firstname.style.backgroundColor=povinne_barva;
        return false;
    } 
    else if (formular.surname.value == "")
    {
        alert("Vyplňte Vaše příjmení.");
        formular.surname.focus();
        formular.surname.style.backgroundColor=povinne_barva;
        return false;
    }             
    else if (formular.email.value == "")
    {
        alert("Vyplňte email.");
        formular.email.focus();
        formular.email.style.backgroundColor=povinne_barva;
        return false;
    }
    else if (formular.email.value != "")
    {
        var re = new RegExp("^[^.]+(\.[^.]+)*@([^.]+[.])+[a-z]{2,4}$");
        if (!re.test(formular.email.value))
        {
            alert("Zadali jste neplatný formát Vašeho emailu!");
            formular.email.focus();
		        formular.email.style.backgroundColor=povinne_barva;
            return false;
        }
    }        
    else
      return true;
}