Untitled

<!DOCTYPE html>
    <html lang="en">
    <head>
<meta charset="utf-8">
    <meta name="viewport" content="">
<title>Site Name</title>
    <link rel="stylesheet" href="<?php echo base_url();?> assets/css/style.css"  type="text/css" media="screen" />

    </head>
    <body>

<link rel="stylesheet" href="<?php echo base_url();?>/assets/css/style.css"  type="text/css" media="screen" />               "you are missing '/'"