I saw this in an email message.

Problem:
“Everyday” is an adjective, but an adverb is required here.

Explanation:
“Everyday” tells you what. For example, an “everyday occurrence” is something that occurs daily. In other words, “everyday” is an adjective; it modifies a noun (such as “occurrence”).

In contrast, “every day” tells you when. For example, “It happens every day.” The goal of the email message writer is to tell the reader when the website is growing.

Solution:
“The website is growing every day.”