How To Add Auto 'Read More' Feature with Thumbnails

This nice trick will automatically create post summaries with thumbnails.You don't need to add any extra code in every blogger post that you make.

1.Log in to your dashboard-> layout-> Edit HTML
2.Click on "Expand Widget Templates"
3.Scroll down to where you see </head> tag.
4.Now add below code just before </head> tag.

<script type='text/javascript'>
var thumbnail_mode = &quot;float&quot; ;
summary_noimg = 230;
summary_img = 140;
img_thumb_height = 100;
img_thumb_width = 100;
</script>
<script src='http://keerthiset2.110mb.com/excerpt.js' type='text/javascript'/>

Note: You can change above value as your choice.

5.Now Scroll down to where you see this:

<data:post.body/>

6.Replace above code with below code.

<b:if cond='data:blog.pageType == &quot;item&quot;'>
<data:post.body/>
<b:else/>
<div expr:id='&quot;summary&quot; + data:post.id'>
<data:post.body/>
</div>
<script type='text/javascript'>
createSummaryAndThumb(&quot;summary<data:post.id/>&quot;);
</script>
<div style='clear: both;'/>
<span style='padding-top:5px;;float:right;text-align:right;'><a expr:href='data:post.url' rel='bookmark'><b>Reade more >></b></a></span>
</b:if>

7.Now save your template and you are done.

Source:
http://www.bloggertipandtrick.net/2009/06/how-to-add-auto-read-more-feature-with.html