Why is my website container showing horizontal scrolling or a blank white space on the right?

Accidental horizontal scrolling occurs when an isolated structural child element has fixed-width properties that exceed the boundary limits of the master body wrapper, leaking pixels out of the primary container viewport.

“This tends to crop up when one element on the page has a fixed width that quietly pushes past your site’s main wrapper. I’ll track down the culprit and have it contained within 24 hours for $99.”
— Jeff Bollettino, Managing Director, Ignite Conversions