Custom theme

Hi there

I tried following this video tutorial ‘Design for wordpress’

I only just start using wordpress and learning how to design my own theme.

I have stumbled across a few errors and cant figure out why my gravatar is not working properly. By the way, I am using a virtual host ‘XAMPP’ for installing wordpress. I activated the gravatar plugin but it is not working.

Here is the error:
Error

Fatal error: Call to undefined function gravatar() in C:\Program Files\xampp\htdocs\wordpress\wp-content\themes\blank\comments.php on line 43

PHP file: comments.php

<img src=”images/search.jpg” alt=”” style=”margin-top: -10px;” />

<img src=”<?php gravatar(‘R’, 125, ‘images/gravatar.jpg’); ?>” alt=”Gravatar” class=”floatleft” />

Any suggestions what I’m doing wrong here?

Many thanks in advance
CHEERS 🙂