As you have to sell your products and services to the internet community then you also have to understand them, if you don't understand them then it would become very hard to sell anything.
You have to understand which kind of products and services demanded on internet, what should be pricing for that so that your products would sell good. What kind of pages you have write mentioning details of your products so that your writing would attract customers and lot more other things as well.
You may also need to communicate through emails and you should have strong communication skill, which should be of global level communication.
And lot more other things you have to follow if you want to be a successful internet marketer..