>Hi everybody,
>
>I am wondering if there is some online dictionary where I can check if I used the right preposition in a phrase? Say, often after I've written a phrase I have a feeling that something is not exactly right. I want to be able to quickly check myself.
>
>Thanks in advance.

If you don't know it yet, have a look at : "The Elements of Style" by William Strunk Jr and E.B. White. It's just about 85 pages. Admittedly there are a lot of exceptions, but there are also a few rules that are very succinctly outlined in the book.

And don't ask why I do not apply everything I might have read (some 30 years ago) in that book. :)

Hope this helps and kind regards,

Marc