I was asking if the following code has a correct semantically markup, or can it better, and so yes, how:
<!-- Start container website -->
<header id="header">
<div class="container_12">
<div class="grid_12">
<a href="#" id="logo"><img src="images/logo.png" alt="Logo"></a>
<a href="#" id="nav-icon"><img src="images/list-icon.png" alt="Responsive list icon"></a>
<nav id="primary-navwrapper" class="inactive">
<ul id="listnav">
<li><a href="index.html" id="current">Home</a></li>
<li><a href="pages/portfolio.html">Portfolio</a></li>
<li><a href="pages/blog.html">Blog</a></li>
<li><a href="pages/service.html">Service</a></li>
<li><a href="pages/about.html">About</a></li>
<li><a href="pages/contact.php">Contact</a></li>
</ul><!-- End ul#listnav -->
</nav><!-- End nav#primary-navwrapper -->
</div><!-- End div.grid_12 -->
<div class="clear"></div><!-- End div.clear -->
</div><!-- End div.container_12 -->
</header><!-- End header#header -->
<div id="container">
<section id="hero">
<div class="flexslider">
<ul class="slides">
<li>
<img src="images/flexslider/slide-1.jpg" alt="" />
<div class="flex-caption">
<div class="container_12">
<header class="grid_12">
<h1>Fris. Responsive. Retina Ready.</h1>
<p>
Donec sed odio dui. Nulla vitae elit libero, a pharetra augue. Nullam id dolor id nibh ultricies vehicula ut id elit.
Integer posuere erat a ante venenatis dapibus posuere velit aliquet.
</p>
<a href="#" class="button tertiaire custom">Read the blog →</a>
</header><!-- End header.grid_12 flex-caption -->
<div class="clear"></div><!-- End div.clear -->
</div><!-- End div.container_12 -->
</div><!-- End div.flex-caption -->
</li>
<li>
<img src="images/flexslider/slide-5.jpg" alt="" />
</li>
</ul><!-- End ul.slides -->
</div><!-- End div.flexslider -->
</section><!-- End section#hero -->
<section id="introduce">
<div class="container_12">
<ul id="featured-list">
<li class="grid_4 centered">
<img src="images/branding.png" alt="Branding & Logo">
<h3>Branding & Logo</h3>
<p>
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<br>
<br>
Vivamus aliquam semper sapien, quis aliquet purus rutrum id.
</p>
</li><!-- End li.grid_4 -->
<li class="grid_4 centered">
<img src="images/webdesign.png" alt="Web Design">
<h3>Web Design</h3>
<p>
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<br>
<br>
Vivamus aliquam semper sapien, quis aliquet purus rutrum id.
</p>
</li><!-- End li.grid_4 -->
<li class="grid_4 centered">
<img src="images/webdevelopment.png" alt="Web Development">
<h3>Web Development</h3>
<p>
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<br>
<br>
Vivamus aliquam semper sapien, quis aliquet purus rutrum id.
</p>
</li><!-- End li.grid_4 -->
</ul><!-- End ul#featured-list -->
<div class="grid_12">
<div id="flick-through">
<div id="placer"><img src="images/flick/flick.jpg" alt=""></div>
<ul id="image-loop">
<li><img src="images/flick/image-1.jpg" alt=""></li>
<li><img src="images/flick/image-2.jpg" alt=""></li>
<li><img src="images/flick/image-3.jpg" alt=""></li>
<li><img src="images/flick/image-4.jpg" alt=""></li>
<li><img src="images/flick/image-5.jpg" alt=""></li>
<li><img src="images/flick/image-6.jpg" alt=""></li>
<li><img src="images/flick/image-7.jpg" alt=""></li>
<li><img src="images/flick/image-8.jpg" alt=""></li>
</ul><!-- End #image-loop -->
</div><!-- End div#flick-through -->
<img src="images/large-cinema-display.png" alt="Cinema Display" id="cinema-display">
</div><!-- End div.grid_12 -->
<div class="clear"></div><!-- End div.clear -->
</div><!-- End div.container_12 -->
</section><!-- End section#introduce -->
<hr>
<section id="portfolio-entry" class="alt">
<div class="container_12">
<header class="centered">
<h1>Latest work</h1>
<p>
Donec sed odio dui. Nulla vitae elit libero, a pharetra augue. Nullam id dolor id nibh ultricies vehicula ut id elit.
<br>
Integer posuere erat a ante venenatis dapibus posuere velit aliquet.
</p>
</header><!-- End header.centered -->
<ul class="entrybox">
<li class="grid_4 portfolio-post">
<header class="post-thumb">
<a href="#"><img src="images/portfolio-thumb.png" alt="Post thumbnail"></a>
</header><!-- End header.post-thumb -->
<aside>
<h3><a href="#" title="">Title Project</a></h3>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
</aside><!-- End aside -->
</li><!-- End li.grid_4 portfolio-post -->
<li class="grid_4 portfolio-post">
<header class="post-thumb">
<a href="#"><img src="images/portfolio-thumb.png" alt="Post thumbnail"></a>
</header><!-- End header.post-thumb -->
<aside>
<h3><a href="#" title="">Title Project</a></h3>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
</aside><!-- End aside -->
</li><!-- End li.grid_4 portfolio-post -->
<li class="grid_4 portfolio-post">
<header class="post-thumb">
<a href="#"><img src="images/portfolio-thumb.png" alt="Post thumbnail"></a>
</header><!-- End header.post-thumb -->
<aside>
<h3><a href="#" title="">Title Project</a></h3>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
</aside><!-- End aside -->
</li><!-- End li.grid_4 portfolio-post -->
</ul><!-- End ul.entrybox -->
<div class="grid_12">
<a href="#" class="button primary">View the Portfolio →</a>
</div><!-- End div.grid_12 -->
<div class="clear"></div><!-- End div.clear -->
</div><!-- End div.container_12 -->
</section><!-- End section#portfolio-entry .alt -->
<hr>
<section id="blog-entry">
<div class="container_12">
<header class="centered">
<h1>Recent blog posts</h1>
<p>
Donec sed odio dui. Nulla vitae elit libero, a pharetra augue. Nullam id dolor id nibh ultricies vehicula ut id elit.
<br>
Integer posuere erat a ante venenatis dapibus posuere velit aliquet.
</p>
</header><!-- End header.centered -->
<ul class="entrybox">
<li class="grid_12 blog-post">
<header class="post-thumb">
<a href="#"><img src="images/blog-thumb.png" alt="Post thumbnail"></a>
</header><!-- End header.post-thumb -->
<aside class="entry-post">
<span class="capitalize">Entry</span>
<h1 class="entry-title">
<a href="#" title="">Fris. Responsive. Retina Ready.</a>
</h1><!-- End h2 .entry-title -->
<ul class="entry-meta">
<li class="author">
By <a href="#">Casper Biemans</a>
</li>
<li class="published">
On <a href="#">September 1, 2012</a>
</li>
<li class="entry-categories">
In <a href="#">Digital Art</a>
</li>
<li class="comment-count">
With <a href="#">22 Comments</a>
</li>
<li class="permalink">
<img src="images/permalink_icon.png" alt="Permalink post"> <a href="#">Permalink</a>
</li>
</ul><!-- End ul.entry-meta -->
</aside><!-- End aside.entry-post -->
</li><!-- End li.grid_12 blog-post -->
<li class="grid_12 blog-post">
<header class="post-thumb">
<a href="#"><img src="images/blog-thumb.png" alt="Post thumbnail"></a>
</header><!-- End header.post-thumb -->
<aside class="entry-post">
<span class="capitalize">Entry</span>
<h1 class="entry-title">
<a href="#" title="">Fris. Responsive. Retina Ready.</a>
</h1><!-- End h2 .entry-title -->
<ul class="entry-meta">
<li class="author">
By <a href="#">Casper Biemans</a>
</li>
<li class="published">
On <a href="#">September 1, 2012</a>
</li>
<li class="entry-categories">
In <a href="#">Digital Art</a>
</li>
<li class="comment-count">
With <a href="#">22 Comments</a>
</li>
<li class="permalink">
<img src="images/permalink_icon.png" alt="Permalink post"> <a href="#">Permalink</a>
</li>
</ul><!-- End ul.entry-meta -->
</aside><!-- End aside.entry-post -->
</li><!-- End li.grid_12 blog-post -->
</ul><!-- End ul.entrybox -->
<div class="grid_12">
<a href="#" class="button primary">View the Blog →</a>
</div><!-- End div.grid_12 -->
<div class="clear"></div><!-- End div.clear -->
</div><!-- End div.container -->
</section><!-- End section#blog-entry -->
<section id="twitter" class="alt">
<div class="container_12">
<div class="grid_12 centered">
<img src="images/twitter.png" alt="Tweet birdie">
<article id="tweet"></article>
<p>You should follow us on <a href="#">Twitter</a> for our latest updates.</p>
</div><!-- End div.grid_12 centered -->
<div class="clear"></div><!-- End div.clear -->
</div><!-- End div.container_12 -->
</section><!-- End section#twitter -->
<hr>
<section id="hire-me">
<div class="container_12">
<div class="grid_8">
<h3>Get in touch</h3>
</div><!-- End div.grid_8 -->
<div class="grid_4 button-group">
<a href="#" class="button tertiaire grid_2">About</a>
<a href="#" class="button tertiaire custom grid_2">Contact</a>
</div><!-- End div.grid_4 -->
<div class="clear"></div><!-- End div.clear -->
</div><!-- End div.container_12 -->
</section><!-- End section#hire-me -->
</div><!-- End div#container -->
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