1)Con ayuda de lenguaje de servidor:
Código PHP:
<?php
session_start();
if(isset($_GET['im'])){
header("Content-type:image/gif");
$im='R0lGODlhlgAyAIAAAP///wAAACH5BAEAAAAALAAAAACWADIAAAJghI+py+0Po5y02ouz3rz7D4biSJbmiabqyrbuC8fyTNf2jef6zvf+DwwKh8Si8YhMKpfMpvMJjUqn1Kr1is1qt9yu9wsOi8fksvmMTqvX7Lb7DY/L5/S6/Y7P6/f8/r4AADs=';
echo base64_decode($im);
$_SESSION['activado']='si';
exit;
}
if(isset($_GET['verificar'])){
if($_SESSION['activado']=='si'){
echo '
alert("css activado");
';
}else{
echo '
alert("css desactivado");
';
}
exit;
}
if(isset($_GET['recargar'])){
$_SESSION['activado']='no';
exit;
}
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>ver css</title>
<script>
function rpc(url){
oldsc=document.getElementById("old_sc");
if(oldsc)
document.getElementsByTagName('body')[0].removeChild(oldsc);
sc=document.createElement('script');
sc.id="old_sc";
sc.src=url+'&'+Math.random();
document.getElementsByTagName('body')[0].appendChild(sc);
}
function addCss(cssCode,i) {
control=document.getElementById(i)
if(control)
document.getElementsByTagName("head")[0].removeChild(control)
var styleElement = document.createElement("style");
styleElement.type = "text/css";
if (styleElement.styleSheet) {
styleElement.styleSheet.cssText = cssCode;
} else {
styleElement.appendChild(document.createTextNode(cssCode))
}
styleElement.id =i;
document.getElementsByTagName("head")[0].appendChild(styleElement);
}
window.onload=function(){
rpc('<?php echo basename($_SERVER['PHP_SELF']) ?>?recargar');
old=document.getElementById("pp");
if(old)
document.getElementsByTagName("body")[0].removeChild(old);
o=document.createElement('div');
o.id='pp';
o.className='ver';
document.getElementsByTagName('body')[0].appendChild(o);
cssCode='.ver{background:url(<?php echo basename($_SERVER['PHP_SELF']) ?>?im);}';
addCss(cssCode,'tester');
setTimeout("rpc('<?php echo basename($_SERVER['PHP_SELF']) ?>?verificar')",200);
}
</script>
</head>
<body>
</body>
</html>
2)CSS y Modelo de Cajas Correcto (importante usar doctype adecuado):
Código PHP:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>test</title>
<script>
function testBoxModel(){
var test = document.createElement('div');
test.style.visibility = 'hidden';
test.style.width = '100px';
test.style.padding = '100px';
document.getElementsByTagName('body')[0].appendChild(test);
var w = test.offsetWidth || 0;
if(w!=300) {return false;}
document.getElementsByTagName('body')[0].removeChild(test);
return true;
}
onload=function(){
if(!testBoxModel()){alert('incorrecto modelo de cajas o css desactivado');}
}
</script>
</head>
<body>
</body>
</html>