// JavaScript Document

function fncEnviar() { 

 var f = document.faleconosco;
 
 	if(f.nome.value == '') { 
		alert('Preencha campo nome');
		return false;
	}
	else if(f.email.value == '') { 
		alert('Preencha o campo email');
		return false;
	}
	else if(f.mensagem.value == '') { 
		alert('Preencha a mensagem');
		return false;
	}
	else { 
		f.action = 'enviaEmail.asp';
		f.submit();
	}

}



<!--
function MM_swapImgRestore() { //v3.0
  var i,x,a=document.MM_sr; for(i=0;a&&i<a.length&&(x=a[i])&&x.oSrc;i++) x.src=x.oSrc;
}

function MM_preloadImages() { //v3.0
  var d=document; if(d.images){ if(!d.MM_p) d.MM_p=new Array();
    var i,j=d.MM_p.length,a=MM_preloadImages.arguments; for(i=0; i<a.length; i++)
    if (a[i].indexOf("#")!=0){ d.MM_p[j]=new Image; d.MM_p[j++].src=a[i];}}
}

function MM_findObj(n, d) { //v4.01
  var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
    d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}
  if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
  for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers[i].document);
  if(!x && d.getElementById) x=d.getElementById(n); return x;
}

function MM_swapImage() { //v3.0
  var i,j=0,x,a=MM_swapImage.arguments; document.MM_sr=new Array; for(i=0;i<(a.length-2);i+=3)
   if ((x=MM_findObj(a[i]))!=null){document.MM_sr[j++]=x; if(!x.oSrc) x.oSrc=x.src; x.src=a[i+2];}
}

function mostrar(el) {
	document.getElementById(el).style.visibility = "visible";
}
function esconder(el) {
	document.getElementById(el).style.visibility = "hidden";
}

function imagens_random() {
	var img = new Array();

	// aqui você lista as imagens que serão randomizadas (obs: comece do 0)
	 
	img[0] = 'img_parceiros01.jpg';
	img[1] = 'img_parceiros02.jpg';
	img[2] = 'img_parceiros03.jpg';
	 
	rnd = Math.floor(Math.random()*img.length);
	
	document.getElementById("img").src = "images/" + img[rnd];
}
//-->

MM_preloadImages('images/bt_home_over.jpg','images/bt_empresa_over.jpg','images/bt_parceiros_over.jpg','images/bt_servicos_over.jpg','images/bt_faleconosco_over.jpg')