Add a button in any post for bloggers, such as slightly different than adding a button Web sites like Facebook. Like take a look at how to add button to every post. Is the most reliable used up to now this technique.
You go to Facebook developers and your url, your style generates part of the code. Make sure you can easily see and does not contain http:// in to the url of your.
Now goto your blog and edit it's template in HTML i.e  Design >>> Edit HTML.
make sure you check expand widget templates.

now find <data:post.body/>
and after this line write
<div class ='facebooklike'>

and paste you code in this div.
After pasting your code replace starting tags with &tl; and ending tags with &gt;
( < with &lt; and > with gt; ) and your url with <div:post.url/>.
Your code should look something like this.
Click Save Template and you're done now.