Good Grammer "are" Important

Sales literature for the XYZ Skylight Company boosts that the firm offers "consistent quality" and their structural drawings are "professionally reviewed."  Unfortunately, their sales corresponsdence and literature demonstrates neither of these attributes.

A recent cover letter introducing the company contains numerous grammar and spelling errors. For example, the letter's first paragraph states:
"XYZ is a manufacturer of commercial heavy-duty skylights; who delivers and installs."
Maybe they mean that they, "also deliver and install their product," but who knows?
"Our skylight systems is designed based on the principals of pressure equalization, more commonly known as the rain screen principal."
As my junior high school English teacher drilled into me, the, "The principle is that the principal is your pal."

There are similar errors in the company's brochure, too.

Recommendation: Don't rely on your computer's spell checker alone. Have your sales correspondence and literature copy edited by someone with the talent for catching errors. If you don't, your customers will. (Specifiers are especially keen on spotting mistakes of this kind.)