Generic or custom layout?
Layout is one of your most important design decisions while creating a website. It is bound with proper understanding of what needs to be done (customer requirements), what the site will contain (type of information and its organization), graphics, proper font and color scheme.
Many web design companies offer ready templates online. These inexpensive layouts allow customers to build up a site almost immediately. They only need to apply their content to the existing layout. If price is crucial or the site is not for serious purposes, that is a good way to quickly provide a content to a large audience.
Custom layouts do not rely on ready templates. Their timing is more accurate and may make a website unique on its own. Such layouts are created for specific customer needs and are therefore more suitable for serious purposes. Their flexibility allows them to integrate more advanced futures (such as content management system or payment system), to emphasize on corporate identity and to achieve more polished look considering even the smallest details. A disadvantage is that they are developed at a slower pace, and may require sometimes months to complete. Because they are consuming more time, the customer is charged much more than for a generic layout.
Why not use them both?
I have decided to use only custom layouts on my sites.