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Well this is a tough question because while many sites for commercial purposes have been done with iweb it was not its primary purpose and it is lacking some features that you may need. Depending on the type of business and what you want to accomplish it is possible to do so but your question is not very clear as to what you need.
Then there is the other problem, according to terms of agreement you are not permitted to have a commercial site on .mac. I have seen a few with what could be called a commercial bent but not a high traffic type site. If you are going to need the traffic you would be better off on another server anyway since .mac can be a little slow at times. I cannot say how will me be so far it is a mess.
 
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