When did grammar, spelling and sentence construction get in the way of creativity? Look at all the work that has gone before you, look at the authors that are being published now.
Writing on here really doesn't call for great grammar; however, getting it right will improve the experience of any reader.
I liked the explanation that Ray Bradbury gave, a long time ago; he called it the writer's blurt: When you get an idea, just write it down, fast, furious, don't let the brain stop and think, then put it in the drawer for a few weeks before you read it again, then you can sort it out, but not so much as to kill it, but enough for it to get past the editor.
The editor is the one who counts if you want to sell your work, especially to print publishers, and an awful lot of content publishers on the web also require perfect grammar and spelling.
For hubpages, I think Junkseller has it about right.