>>>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.
>>
>>That's not going to be an easy task. You know how to diagram a sentence? Might look here: http://www.english-grammar-revolution.com/prepositional-phrase.html
>>
>>There is a preposition in a phrase - but there is also something called a prepositional phrase.
>
>And what is the difference?

Well one is a word the other is a whole phrase.

So if you have this:
"At home."

"At" = preposition;
"home" = noun.
"At home." = prepositional phrase.