function CheckContact(){
	var Ok=true;
	
	// custom variables
	var name = window.document.getElementById('txtIme');
		var nameError = window.document.getElementById('nameError');
	var mail = window.document.getElementById('txtEmail');
		var mailError = window.document.getElementById('mailError');
	var message = window.document.getElementById('txtPoruka');
		var messageError = window.document.getElementById('messageError');
	var grForm = window.document.getElementById('grForm');
	var number = window.document.getElementById('number');
		var numberError = window.document.getElementById('captchaError');
	
	// defalut CSS classes and states
	name.className="textbox";
		nameError.innerHTML = "";	
	mail.className="textbox";
		mailError.innerHTML = "";	
	message.className="textarea";
		messageError.innerHTML = "";
	grForm.style.display='none';
	number.className="textbox";
		numberError.innerHTML = "";
		
	// validate empty fields (name, mail)
	var required = new Array(name,mail,number);	
	for (i=0;i<required.length;i++) {
		if ((required[i].value == "") || (required[i].value.length==0)){
			required[i].className = "textbox_error";
			Ok = false;
		}
	}
	
	// name error notification
	if((name.value == "") || (name.value.length==0)){
		name.className='textbox_error';
		nameError.innerHTML = "Ime je obavezno polje.";
		Ok = false;
	}
	
	// textarea validation
	if((message.value == "") || (message.value.length==0)){
		message.className='textarea_error';
		messageError.innerHTML = "Napišite nam poruku, mi ćemo Vam odgovoriti.";
		Ok=false;
	}
	
	// empty captcha
	if((number.value == "") || (number.value.length==0)){
		numberError.innerHTML = "Pažljivo ponovite karaktere sa slike!";
		Ok=false;
	}
	
	// mail pattern
	var mailFileter = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/;
	if (!mailFileter.test(mail.value)){			
		mail.className = "textbox_error";
		mailError.innerHTML = "Upišite validnu email adresu!";
		Ok = false;
		}
		
	// main error message
	if(!Ok){
		grForm.style.display='';
		}
return Ok;
}