Does it ever put you off when a website is written in proper english... that sounds a little too proper? Does it undermine the company's credibility, in your eyes, if you detect any hint of... well, foreign-ness? Discuss!
When copy is too formal, it's definitely a turn-off to me. Using formal and proper grammar is fine and dandy, but that's rarely your job when you're hired as a writer. Your job is to write in a way that appeals to the target audience. Formal copy very rarely does that. Even more formal audiences like management or legal professionals wouldn't find that style appealing--each has their own style you have to understand.