JS: Cookie fout (help)

<script type="text/javascript" >
var one_time=true; // true: wordt eenmalig getoond , false: bij iedere pageload.

var splash_string="showit()";
function showit(hs){
// ------------[ tbv splash lightbox] ---------
var t="block"
if (hs==0) t="none"
document.getElementById('light').style.display=t;
document.getElementById('fade').style.display=t;
}
function get_cookie(Name) {
//------------------------------
var search = Name + "="
var returnvalue = "";
if (document.cookie.length > 0) {
offset = document.cookie.indexOf(search)
if (offset != 1) { // if the cookie exists
offset += search.length
//set the index of beginning value
end = document.cookie.indexOf(";", offset);

if (end == -1) // set the index of the end of cookie value
end = document.cookie.length;
returnvalue = unescape(document.cookie.substring(offset, end))
}
}
return returnvalue;
}
function loadornot(){
if (get_cookie('splash')==''){
eval(splash_string);
document.cookie="splash=yes"
}
}
window.onload=function(){
//------------------
window.focus();
if (one_time==false){ eval(splash_string);
}else{ loadornot();}
}
</script >

document.cookie="splash=yes"

var expirationDate = new Date;
expirationDate.setMonth(expirationDate.getMonth()+6);
document.cookie = 'splash=yes; expires='+expirationDate.toGMTString()+'; path=/'