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

2.Don't Click on "Expand Widget Templates"

3.Scroll down to where you see ]]></b:skin> tag:

4.Copy below code and paste it just before the ]]></b:skin> tag.

/* pageTabs
*/
.pageTabs {width: 760px; height:150px; margin: 10px auto 0;  font-size:11px;}
ul.tabs {
margin: 0;
padding: 0;
float: left;
list-style: none;
height: 32px;
border-bottom: 1px solid #999;
border-left: 1px solid #999;
width: 100%;
}
ul.tabs li {
float: left;
margin: 0;
padding: 0;
height: 31px;
line-height: 31px;
border: 1px solid #999;
border-left: none;
margin-bottom: -1px;
background: #e0e0e0;
overflow: hidden;
position: relative;
}
ul.tabs li a {
text-decoration: none;
color: #000;
display: block;
font-size: 1.2em;
padding: 0 20px;
border: 1px solid #fff;
outline: none;
}
ul.tabs li a:hover {
background: #ccc;
}
html ul.tabs li.active, html ul.tabs li.active a:hover  {
background: #fff;
border-bottom: 1px solid #fff;
}
.tab_container {
border: 1px solid #999;
border-top: none;
clear: both;
float: left;
width: 100%;
background: #fff;
-moz-border-radius-bottomright: 5px;
-khtml-border-radius-bottomright: 5px;
-webkit-border-bottom-right-radius: 5px;
-moz-border-radius-bottomleft: 5px;
-khtml-border-radius-bottomleft: 5px;
-webkit-border-bottom-left-radius: 5px;
}
.tab_content {
padding: 20px;
font-size: 1.2em;
}
.tab_content h2 {
font-weight: normal;
padding-bottom: 5px;
border-bottom: 1px dashed #ddd;
font-size: 1.8em;
}
.tab_content h3 a{
line-height: 2em;
color: #254588;
}
.tab_content img {
float: left;
margin: 10px 20px 20px 0;
border: 1px solid #ddd;
padding: 5px;
}
.tab_content p{
padding-bottom:10px;
}
/*

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

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

<script src='http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js' type='text/javascript'/>

<script type='text/javascript'>
$(document).ready(function(){$(&quot;.tab_content&quot;).hide();$(&quot;ul.tabs li:first&quot;).addClass(&quot;active&quot;).show();$(&quot;.tab_content:first&quot;).show();$(&quot;ul.tabs li&quot;).click(function(){$(&quot;ul.tabs li&quot;).removeClass(&quot;active&quot;);$(this).addClass(&quot;active&quot;);$(&quot;.tab_content&quot;).hide();var activeTab=$(this).find(&quot;a&quot;).attr(&quot;href&quot;);$(activeTab).fadeIn(1000)})});
</script>

7.Now Click on "Save Templates"

8.Now go to Layout-->page elements and Click on 'Add a Gadget'.

9.Now Select 'HTML/Javascript' and add the code given below and click save.

<ul class="tabs">
<li><a href="#tab1">TAB1</a></li>
<li><a href="#tab2">TAB2</a></li>
<li><a href="#tab3">TAB3</a></li>
<li><a href="#tab4">TAB4</a></li>
<li><a href="#tab5">TAB5</a></li>
</ul>

<div class="tab_container">
<div id="tab1" class="tab_content">
ENTER TAB 1 CONTENT
</div>

<div id="tab2" class="tab_content">
ENTER TAB 2 CONTENT
</div>

<div id="tab3" class="tab_content">
ENTER TAB 3 CONTENT
</div>

<div id="tab4" class="tab_content">
ENTER TAB 4 CONTENT
</div>

<div id="tab5" class="tab_content">
ENTER TAB 5 CONTENT
</div>

</div>

Now you are done.It will look like this :