This year's PubCon Search Personality of the Year is Melissa Fach. She posted the slides from one of her talks/workshops and this one applies to everyone who writes content. It's very good and worth taking the time to see.
Some Truths… We remember who you are. And, editors across publications talk – often.
Personal Pet Peeves: Contractions Too many contractions will make an article sound casual and not authoritative. And, people don’t read in their heads the way that they speak.
My rule of thumb is that it is okay to relax somewhat in a personal blog but for ALL professional writing, articles, marketing content and content I want taken seriously, no contractions.
I see more websites than most people due to my work and one of the UX criteria for credibility and authenticity is readability and the quality of writing. I always need editors to look over my work. It is a lesson I learned when I worked for a magazine publisher.