By default joomla shows a number by each article when listing all the titles in a category view layout.

Here's how to remove the numbers...

 

Navigate to /components/com_content/views/category/tmpl/default_items.php and download the file.

To overide the file we need to copy it to the template folder. If it doesn't already exist, create the folder:

/templates/yourtemplatename/html/com_content/category/

Open up the file and locate the line:

<?php echo $this->pagination->getRowOffset( $item->count ); ?>

Comment it out by changing it to:

<!--<?php echo $this->pagination->getRowOffset( $item->count ); ?>-->

This will remove the numbers by each article.

To remove the # in the head, locate the line:

<?php echo JText::_('Num'); ?>

And replace with:

<!--<?php echo JText::_('Num'); ?>-->

If you want to reduce the width of the column, just reduce the 5% in the line above to 1%

Save the file and upload it to

/templates/yourtemplatename/html/com_content/category/default_items.php

It should now look something like this