So you've got a great idea that you want to tell the world about? Don't care too much about spelling or grammar while writing about it? That's where you let your great idea down.
Let's say your great idea is like a great guy who's going to a job interview. He really is the perfect candidate, there's nothing that could prevent him from being hired – just like your idea is so good that everyone should understand it right away and give you the praise you deserve for coming up with it.
There's just one thing, the suit the guy is wearing is a bit wrinkled (and you've written "it's" where you should have written "its"). Not a big problem, you say, everyone can have a bad day. Then you notice that Great Guy's fly is undone (and you've written "whose" where you should have written "who's"). "Not to worry", you say, "he's still a great guy and everyone who listens to him will realize that".
If this was all, it probably wouldn't have been a big deal. It's just that he's also forgotten to brush his teeth, he didn't have time to shower, and while eating a hot dog on the way to the interview he spilled some ketchup on his shirt. Then, as he was getting out of the cab outside the building, he slipped and fell into a puddle of muddy sleet…
Soon enough your Great Guy looks more like a bum than anything else, and nobody will take anything he says seriously. So please don't dress your ideas like bums – present them in a way that lets them be judged on their own merit and not on your sloppy grammar!