Differences between the US and British (in Grammar)

In my mind I wanted to write about people who get their grammar wrongly, while I was surfing the net I found this instead article about 'present perfect difference American British English grammar'.

"What's the difference between the US and British use of the present perfect?"

Although there are few grammatical differences between British and American English (as opposed to differences in vocabulary, which are many), this is, perhaps, the main one.

The answer is simple. Americans will often use the past simple tense where a British speaker would use the present perfect tense. An American will ask:

Did you have dinner yet?
whereas a British person would ask:

Have you had dinner yet?

You can read more about the 'Differences Between American and British English' @ About.com.