It looks like the slider you’re using is adding the CSS and javascript for the slider directly into the section with the slider instead of where they’re supposed to go (CSS in the <head>
, JS in the footer).
WordPress is then wrapping the CSS and JS in a paragraph tag (as WP does to all elements in the editor).
It also has text-align: center on it, so if you view the Text tab you might be able to see it.
If you do, add margin:0 to it: <p style="text-align:center;margin-bottom:0;">
But really, you should be using a slider that adds scripts and styles correctly – your website will be faster.