function getcss(cssfile){

loadcss = document.createElement('link')
loadcss.setAttribute("href", cssfile)
loadcss.setAttribute("rel", "stylesheet")
loadcss.setAttribute("type", "text/css")
loadcss.setAttribute("media", "all")

document.getElementsByTagName("head")[0].appendChild(loadcss)
}

if(screen.width <= '800')
// alt mindre end 800 pixels width

{
getcss('css/bookdefault.css')
// loader css
}

else if(screen.width == '1024' && screen.height == '768')
//res 1024x768

{
getcss('css/book1024x768.css')
//loader css
}

else if(screen.width == '1280' && screen.height == '800')
//res 1280x800

{
getcss('css/book1280x800.css')
//loader css
}

else if(screen.width == '1280' && screen.height == '1024')
//res 1280x1024

{
getcss('css/book1280x1024.css')
//loader css
}

else

{
getcss('css/bookdefault.css')
//hvis ingen af de andre passer, tager den en default
}