Automatically Like a Page
While making a Facebook Page use the following anchor tag to get a user to become a fan of the Page with just one click.

<a ajaxify=”/ajax/pages/fan_status.php?fbpage_id=[Your_Page_ID]&add=1&reload=1&preserve_tab=1&use_primer=1″ rel=”async-post”>Become a Fan</a>
where,
fbpage_id = [Your Page ID], you can get that from the URL of the Page.
reload=1, set to 0 if you don’t want to [...]