Reuven Karasik

This plugin alows you to display a message to all your visitors insode a fancy lightbox. 
features:
<ul>
<li>
Easy interface and simple settings pages
</li>
<li>
All features support any type of client-side code: HTML, Javascript, embed of video or enything you want
</li>
<li>
Display your message to all visitors in a pop-up lightbox. Automaticly put there a like button, and you will get lots of likes every week
</li>
</ul>

Your Lightbox

Display lightbox with your message or like button to all visitors

Carlos Martínez Romero

“Remove Web Field From Comments Form” is a small plugin that allows you remove the web field from all the comments forms so you will never have to deal again with unwanted website links. You can activate it by checking the checkbox at the bottom of Settings > General. This plugin wont work if the value is already defined elsewhere to avoid errors.
<h3>Features</h3>
<ul>
<li>Allow to remove the web field from comments form.</li>
</ul>

Remove Web Field From Comments Form

As the developer of this plugin I created it because I think it should be added into the WP core. Hope you enjoy it. If you are looking for hidding the web field form comment form this is the perfect plugin for you :)

A feaure that should be added into core

This plugin adds a new setting in the last position of Settings > General, this option will allow you to check if you want to remove the web field  …

Your Lightbox vs Remove Web Field From Comments Form