I was placing avast logo’s on my site and then I thought of something cool :)…
I made 1 file with the following source
";
}
elseif($rand == 2)
{
echo "
";
}
elseif($rand == 3)
{
echo "
";
}
elseif($rand == 4)
{
echo "";
}
elseif($rand == 5)
{
echo "
";
}
elseif($rand == 6)
{
echo "
";
}
elseif($rand == 7)
{
echo "
";
}
elseif($rand == 8 )
{
echo "
";
}
elseif($rand == 9 )
{
echo "
";
}
elseif($rand == 10)
{
echo "
";
}
elseif($rand == 11)
{
echo "
";
}
?>
The code is simple… $rand gets a different value everytime this script is loaded. So that means you get a different logo on the page.
And that migth be usefull 
edit: (Only works in php sites ;))