window.onload= initStyle;
window.onunload = unloadStyle;

function initStyle(){
    var thisCookie= cookieVal("style");
    var title=(thisCookie) ? thisCookie : getPreferredStylesheet();
    setActiveStylesheet(title);
    var allButtons = document.getElementsByTagName("input");
    
    for(var i=0; i<allButtons.length; i++){
        if(allButtons[i].type == "image"){
            allButtons[i].onclick= setActiveStylesheet;
        }
    }
}

function unloadStyle(){
    var expireDate = new Date();
    expireDate.setYear(expireDate.getFullYear()+1);
    document.cookie="style="+getActiveStylesheet()+";expires=" +expireDate.toGMTString()+";path=/";
}

function getPreferredStylesheet(){
    var thisLink, relAttribute;
    var linksFound = document.getElementsByTagName("link");
    
    for(var i=0; i<linksFound.length; i++){
        thisLink = linksFound[i];
        relAttribute = thisLink.getAttribute("rel");
        if(relAttribute.indexOf("style") > -1 &&  relAttribute.indexOf("alt") == -1 && thisLink.getAttribute("title")){
                return thisLink.getAttribute("title");
        }
    }
    return "";
}

function getActiveStylesheet(){
    var thisLink;
    var linksFound=document.getElementsByTagName("link");
    
    for(var i=0; i<linksFound.length; i++){
        thisLink = linksFound[i];
        if(thisLink.getAttribute("rel").indexOf("style") > -1 && thisLink.getAttribute("title") && !thisLink.disabled){
            return thisLink.getAttribute("title");
        }
    }
    return "";
}

function setActiveStylesheet(inVal){
    var thisLink;
    var linksFound = document.getElementsByTagName("link");
    
    var title = (inVal) ? 
                    ((typeof inVal == "string") ? 
                            inVal 
                    : inVal.target.id) 
                : window.event.srcElement.id;
    for(var i=0; i<linksFound.length; i++){
        thisLink = linksFound[i];
        if(thisLink.getAttribute("rel").indexOf("style") > -1 && thisLink.getAttribute("title")){
            thisLink.disabled=true;
            if(thisLink.getAttribute("title") == title){
                thisLink.disabled = false;
            }
        }
    }
}




function cookieVal(cookieName){
    var thisCookie = document.cookie.split("; ");
    for(var i=0; i<thisCookie.length; i++){
        if(cookieName == thisCookie[i].split("=")[0]){
            return thisCookie[i].split("=")[1];
        }
    }
    return "";
}