Cara menambah fungsi box pada post

Bismillah, Selama ini saya merasa sulit menulis code dalam textarea,lho mengapa? karena hasilnya akan seperti ini:
<center><div id="menu"><br /><ul><br /><li><a class="current" href="http://k-blogger1.blogspot.com/">home</a></li><br /><li><a href="http://about.com">about us</a></li><br /><li><a href="http://google.com">Google</a></li><br /><li><a href="http://wikipedia.com">Wikipedia</a></li><br /><li><a href="http://k-blogger1.blogspot.com/2010/01/contact-me_14.html">contact us</a></li><br /></ul><br /></div></center><br /><style><br /><br />/* --------------------------<br />AUTHOR : STYLED MENUS<br />URL : http://www.styledmenus.com<br />Copyrights by STYLED MENUS<br />Widget From http://www.ardi33.web.id/<br />----------------------------*/<br />*{<br />margin:0;<br />padding:0;<br /><br />}<br />#menu{<br />background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgX724E8XfGzqETo5u2-rbtMgTamfosA4lUH9BshCR2cYdx8ZRVaft7CDpGq83IaB-ntyf4PWT2Eqf-BnpKESF5gMxyusCMCjIhI0xxQVO-iub6ze1vMpogjq03aCAPR50LO-xa9EbZFB4/s1600/menu_026_bg.jpg) no-repeat;<br />width:172px;<br />height:191px;<br />padding:15px;<br />}<br />#menu ul{<br /><br />list-style:none;<br />padding:0 0 0 8px;<br />}<br />#menu li{<br />list-style:none;<br />display:block;<br />padding:10px 0;<br />}<br />#menu li a{<br /><br />list-style:none;<br />display:block;<br />background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjj_jcmcrIhMW_cuffgOja9mBB1wQc4FRBK7EOyMnku30fXq7YpYj89gx7OeiFLkXqTXy3mBtpZ-enYOe6KKn7_6iOgLfHunQKjwIJt3aajndOmlGCmTSlf7vw1BjAF1rDaX3XKJU4qy5Q/s1600/menu_026_b.gif) no-repeat left center;<br />color:#ffe991;<br />font-weight:bold;<br />text-transform:uppercase;<br />font-size:11px;<br /><br />line-height:1.2em;<br />text-decoration:none;<br />padding:0 5px 0 25px;<br />}<br />#menu li a:hover{<br />background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi42RhSaxcTe6Hv0uGv652vH4q_2-H3KyKSwqwSJTSJTETuYiUVwcj7BMiWSDxu30-JUItL2VTTYiKtA78SPzNnjSeVjy3_XZC6ypMIRRk7p4XCHqj7D44y3Gum-eYxN_q7Zo2t27JLWJM/s1600/menu_026_h.gif) no-repeat left center;<br />color:#fff;<br />text-decoration:none;<br /><br />}<br />#menu li .current{<br />list-style:none;<br />display:block;<br />background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi42RhSaxcTe6Hv0uGv652vH4q_2-H3KyKSwqwSJTSJTETuYiUVwcj7BMiWSDxu30-JUItL2VTTYiKtA78SPzNnjSeVjy3_XZC6ypMIRRk7p4XCHqj7D44y3Gum-eYxN_q7Zo2t27JLWJM/s1600/menu_026_h.gif) no-repeat left center;<br />color:#fff;<br />font-weight:bold;<br />text-transform:uppercase;<br /><br />font-size:11px;<br />text-decoration:none;<br />padding:0 5px 0 25px;<br />}<br />#menu li a.current, #menu li a:hover.current{<br />background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi42RhSaxcTe6Hv0uGv652vH4q_2-H3KyKSwqwSJTSJTETuYiUVwcj7BMiWSDxu30-JUItL2VTTYiKtA78SPzNnjSeVjy3_XZC6ypMIRRk7p4XCHqj7D44y3Gum-eYxN_q7Zo2t27JLWJM/s1600/menu_026_h.gif) no-repeat left center;<br />color:#fff;<br />text-decoration:none;<br /><br />}<br /></style><br />
Dimana setiap baris ada <br />, Coba lihat contoh code yang dimasukkan kedalam box yang sering saya gunakan sebagai pengganti textarea dalam memasukkan code:

<center><div id="menu">
<ul>
<li><a class="current" href="http://k-blogger1.blogspot.com/">home</a></li>
<li><a href="http://about.com">about us</a></li>
<li><a href="http://google.com">Google</a></li>
<li><a href="http://wikipedia.com">Wikipedia</a></li>
<li><a href="http://k-blogger1.blogspot.com/2010/01/contact-me_14.html">contact us</a></li>
</ul>
</div></center>
<style>

/* --------------------------
AUTHOR : STYLED MENUS
URL : http://www.styledmenus.com
Copyrights by STYLED MENUS
Widget From http://www.ardi33.web.id/
----------------------------*/
*{
margin:0;
padding:0;

}
#menu{
background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgX724E8XfGzqETo5u2-rbtMgTamfosA4lUH9BshCR2cYdx8ZRVaft7CDpGq83IaB-ntyf4PWT2Eqf-BnpKESF5gMxyusCMCjIhI0xxQVO-iub6ze1vMpogjq03aCAPR50LO-xa9EbZFB4/s1600/menu_026_bg.jpg) no-repeat;
width:172px;
height:191px;
padding:15px;
}
#menu ul{

list-style:none;
padding:0 0 0 8px;
}
#menu li{
list-style:none;
display:block;
padding:10px 0;
}
#menu li a{

list-style:none;
display:block;
background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjj_jcmcrIhMW_cuffgOja9mBB1wQc4FRBK7EOyMnku30fXq7YpYj89gx7OeiFLkXqTXy3mBtpZ-enYOe6KKn7_6iOgLfHunQKjwIJt3aajndOmlGCmTSlf7vw1BjAF1rDaX3XKJU4qy5Q/s1600/menu_026_b.gif) no-repeat left center;
color:#ffe991;
font-weight:bold;
text-transform:uppercase;
font-size:11px;

line-height:1.2em;
text-decoration:none;
padding:0 5px 0 25px;
}
#menu li a:hover{
background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi42RhSaxcTe6Hv0uGv652vH4q_2-H3KyKSwqwSJTSJTETuYiUVwcj7BMiWSDxu30-JUItL2VTTYiKtA78SPzNnjSeVjy3_XZC6ypMIRRk7p4XCHqj7D44y3Gum-eYxN_q7Zo2t27JLWJM/s1600/menu_026_h.gif) no-repeat left center;
color:#fff;
text-decoration:none;

}
#menu li .current{
list-style:none;
display:block;
background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi42RhSaxcTe6Hv0uGv652vH4q_2-H3KyKSwqwSJTSJTETuYiUVwcj7BMiWSDxu30-JUItL2VTTYiKtA78SPzNnjSeVjy3_XZC6ypMIRRk7p4XCHqj7D44y3Gum-eYxN_q7Zo2t27JLWJM/s1600/menu_026_h.gif) no-repeat left center;
color:#fff;
font-weight:bold;
text-transform:uppercase;

font-size:11px;
text-decoration:none;
padding:0 5px 0 25px;
}
#menu li a.current, #menu li a:hover.current{
background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi42RhSaxcTe6Hv0uGv652vH4q_2-H3KyKSwqwSJTSJTETuYiUVwcj7BMiWSDxu30-JUItL2VTTYiKtA78SPzNnjSeVjy3_XZC6ypMIRRk7p4XCHqj7D44y3Gum-eYxN_q7Zo2t27JLWJM/s1600/menu_026_h.gif) no-repeat left center;
color:#fff;
text-decoration:none;

}
</style>

Bagaimana? Tulisannya sangat teratur bukan?
Jika anda tertarik berikut codenya:

<style>.boxA, .boxB {border-color:#CCCCCC;border-style:solid;border-width:5px 5px 10px;color:#000000;font-family:Arial;font-size:12px;margin:0 auto;overflow:scroll;padding:20px 6px;}.boxA {height:180px;.boxB {height:200</style>
<div class="boxA">
Code yang ingin ditampilkan
</div>

Semoga bermanfaat!