How to add facebook like button after read more
 

I'd like to add a facebook like button at the end of my excerpt, right after the read more text.
I would like to have it there, so it doesn't go below the post image, which is what happens if I put it in the footer.
I'm using the iframe code, since I want to limit the number of plugins. I tried to paste the iframe code at the end of the custom read more code, but I get a strange behavior.
Where should I put this code?

why are you using an iframe?
What is the code?
try wrapping the code in a div like

This is the code I'm using
Is it correct to add it to the custom read more field?
If I used your suggestion I should create a custom style for the facebook like button, right?

Did you try it?

I already tried to enclose the iframe in a div and I got the same result as when not enclosing.
I only wanted to know that the style attribute would have changed. I added it but nothing changed.
Attached you will find a screen capture of what I'm getting.
As you can see the code isn't working. The post is not liked by 4665 people.

It looks like an issue with the iframe code. Why not use a plugin?

I'm trying to limit the number of installed plugins. Moreover, many plugins don't offer enough customization options. Also, if I use the code it is saved in Atahualpa options and it could be easily recovered.