function randomText(len) {
    var available_chars = [];
    for(var i = 48; i < 58; i++) available_chars[available_chars.length] = String.fromCharCode(i);    
    for(var i = 65; i < 91; i++) available_chars[available_chars.length] = String.fromCharCode(i);    
    for(var i = 97; i < 123; i++) available_chars[available_chars.length] = String.fromCharCode(i);    
    if(0==available_chars.length) return false;
    var result="";   
    for(var j=0; j<len; j++) {var ch=available_chars[Math.floor(Math.random()*available_chars.length)]; result+=ch;}
    return result;
}


function reloadCaptcha() {
    var cimg = document.getElementById("img_captcha");
    if (!cimg) return false;
    cimg.src = "gfx/loading3b.gif";
    var rnd = randomText(50);
    cimg.src = "captcha.jpg?" + rnd;
}