Here is a link to a post from some time ago. This presents the points to be taken into account in the design of products that uses mains voltages.
This covers Class I, Class II, types of insulation and the information that has to be included on the rating plate.
IEC 60950 is the harmonised standard most commonly used for IT equipment. Once the manufacturer has satisfied themselves that they meet the standard they would need to produce a DOC (Declaration of Conformity) and apply the CE on the rating plate of the product.
This chapter is an extract from the book "From Prototype to Product" which is available from Amazon worldwide in both print and e-book format.