function $(id) {
return document.getElementById(id);
}

var elem = new Array();
var ident;
    isNS4 = (document.layers) ? true : false;
    isIE4 = (document.all && !document.getElementById) ? true : false;
    isIE5 = (document.all && document.getElementById) ? true : false;
    isNS6 = (!document.all && document.getElementById) ? true : false;

function show(ident) {
	 	 
	 showhide();
	 
	 changeOpac(0, ident);
	 
    if(isNS4) {
    document.layers[ident].display = "";
    }
    else if(isIE4) {
    document.all[ident].style.display = "";
    }
    else if (isIE5 || isNS6) {
    elm = document.getElementById(ident);elm.style.display = "";
    }
	 opacity(ident, 0, 100, 300);
}

function hide(ident) {
	 
	 //opacity(ident, 100, 0, 1000);
	 
    if(isNS4) {
    document.layers[ident].display = "none";
    }
    else if(isIE4) {
    document.all[ident].style.display = "none";
    }
    else if (isIE5 || isNS6) {
    elm = document.getElementById(ident);elm.style.display = "none";
    }
}

function showhide() {
	 hide('oferta');
	  hide('kontakt');
	   hide('ofirmie');
		 hide('realizacje');

}

function toggle(obj) {
	var el = document.getElementById(obj);
	el.style.display = (el.style.display != 'none' ? 'none' : '' );
}

function insertHtml(ident,txt){
   document.getElementById(ident).innerHTML=txt;
}

function next(id)
{
  document.getElementById(id).focus();
  
}

function opacity(id, opacStart, opacEnd, millisec) { 
    //speed for each frame 
    var speed = Math.round(millisec / 100); 
    var timer = 0; 

    //determine the direction for the blending, if start and end are the same nothing happens 
    if(opacStart > opacEnd) { 
        for(i = opacStart; i >= opacEnd; i--) { 
            setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed)); 
            timer++; 
        } 
    } else if(opacStart < opacEnd) { 
        for(i = opacStart; i <= opacEnd; i++) 
            { 
            setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed)); 
            timer++; 
        } 
    } 
} 

//change the opacity for different browsers 
function changeOpac(opacity, id) { 
    var object = document.getElementById(id).style; 
    object.opacity = (opacity / 100); 
    object.MozOpacity = (opacity / 100); 
    object.KhtmlOpacity = (opacity / 100); 
    object.filter = "alpha(opacity=" + opacity + ")"; 
}