An impressive and engaging web design will go a long way to encouraging visitors to pause at your site, but poorly written pages can quickly undo all the design effort. Spelling mistakes, poor punctuation and a lack of clarity will suggest a lack of professionalism and attention to detail.
Copywriting is the term used for writers of compelling text that draws visitors in, gives an impression of professionalism and connects with the target audience.
As well as getting the basics right - spelling, grammar, punctuation, correct use of words in context, paragraph construction and so on - the style of the writing is also important. There is no one 'English' form of writing. A website aimed at professionals in the medical industry, for example, is likely to have its pages worded in a very different style to a site aimed at young petrol heads. Imagine getting the two styles mixed up - you would probably lose your visitors pretty fast!
Many people find it very hard to write about their business, and it's not necessarily because they lack writing skills. It may be just finding the time, and 'writer's block' can be an issue. You know your business back to front but just don't know where to start when it comes to putting it down on paper.