People can change their writing style if they write for a different purpose. When I write fiction, my writing tends to be very tongue-in-cheek, and I take a lot of liberties with grammar, using a lot of fragments, especially in dialogue. When I write for work, there isn't any humor (in the final versions, anyway) and I follow a formal writing style. My friends who read a short story might well guess it is mine. My co-workers who read my professional writing would probably not be able to identify it as mine. Yet I have one co-worker who refuses to split infinitives, no matter how awkward the sentence becomes. He also favors certain words, such as "likely" intead of "may." I can usually tell his writing from those of my other co-workers right away.
Rather than thinking about "your" style and whether it's recognizable, think about the purpose of your writing: to inform, to persuade, to entertain, etc. Then think of your audience. Are you writing in a way that will "speak" to them?
I don't know if there are Web sites, but the best thing to do is just WRITE. Then have your friends and colleagues review your writing to see if you're using a style that is appropriate for your purpose and your audience.