1.Login to your blogger dashboard--> layout- -> Edit HTML

2.Scroll down to where you see </head> tag .

3.Copy below code and paste it just before the </head> tag .

<style type='text/css'>
#tabs26 {
 float:left;
 width:100%;
 background:#000;
 font-size:93%;
 line-height:normal;

 }
#tabs26 ul {
margin:0;
padding:10px 10px 0 50px;
list-style:none;
 }
#tabs26 li {
 display:inline;
 margin:0;
 padding:0;
 }
#tabs26 a {
 float:left;
 background:url(http://2.bp.blogspot.com/_4HKUHirY_2U/SwO0C_gNhKI/AAAAAAAAANU/FMa7w4ZkTs4/left.gif) no-repeat left top;
 margin:0;
 padding:0 0 0 4px;
 text-decoration:none;
 }
#tabs26 a span {
 float:left;
 display:block;
 background:url(http://2.bp.blogspot.com/_4HKUHirY_2U/SwO0GFQwdKI/AAAAAAAAANc/MPQGBY1DG_U/s1600/right.gif) no-repeat right top;
 padding:5px 15px 4px 6px;
 color:#FFF;
 }
#tabs26 a span {float:none;}

#tabsE a:hover span {
 color:#FFF;
 }
#tabs26 a:hover {
 background-position:0% -42px;
 }
#tabs26 a:hover span {
 background-position:100% -42px;
 }
</style>

Note: Please host above 2 images yourself.

4.Now save your template.

5.Go to Layout-->Page Elements and click on "Add a gadget".

6.Select "html/java script" and add the code given below and click save.

<div id="tabs26">

<ul>
<li><a href="#"><span>Home</span></a></li>
<li><a href="#"><span>HTML</span></a></li>
<li><a href="#"><span>CSS</span></a></li>
<li><a href="#"><span>Java Script</span></a></li>
<li><a href="#"><span>About</span></a></li>
<li><a href="#"><span>Contact</span></a></li>
<li><a href="#"><span>Privacy Policy</span></a></li>
</ul>

</div>

You are done.It will look like this:

How To Create Horizontal Menu Using CSS