@sundaridevi, it depends on your visitors, but I have about 2,000 American visitors a day and no complaints about spelling. I also always use British English in forums and no one has every complained (and lots of forums are full of people who do plain about grammar and spelling).
The other thing is that he is almost certainly going to write British English better than American.
Also the British understand American English, but also often find it annoying - as do people from some other English speaking countries. Are visitors better annoyed or puzzled?
I find it really hard to believe that Americans find British English so hard. Some big British sits (the BBC, for example) get huge numbers of American visitors.
@lucy, for a long time "aluminium" was the recommended spelling of the American Chemical Society and it is the recommended spelling of the International Union of Pure and Applied Chemistry. How important that is, depends on your audience, but it does mean that students studying science should know "aluminium".