Website disappeared!

I was trying to fix a problem I am having and came across an article on the web which seemed to address the problem. The article’s instructions were:

It was resolved by adding the following code to the very end of the functions.php:

‘< php add_filter(‘the_excerpt’, ‘do_shortcode’); >’
(Question marks removed from code for this post)

Before trying this, I located the functions.php file in the wp-includes directory. I then copied and pasted the file, renaming the new file functions_org. I then opened functions.php in Wordpad and added the suggested code to the end of the file.

That produced a fatal error when I went to the web site.

So, I deleted the functions.php file, renamed functions_org.php to functions.php and then uploaded the newly renamed file to the server.

New when I go to the website, nothing at all is returned. just a white screen.

I need to get this resolved quickly. Any ideas?