The true mark of a professional business or organization is the quality of its communications. Design is subjective, and a brand can be made to look good any number of ways. But those branding efforts mean little if the words you use to express yourself don't speak to your audience, or worse, are poorly edited for grammar and spelling.
Writing for different media is an art. People intake content differently when reading a Web site versus a magazine, newspaper, billboard, novel or any number of media in which content is prominent. Understanding how to craft language for a specific medium is key to getting your message across effectively.