Web marketing agencies are companies that will build and promote your website and company profile online. Most agencies offer a wide range of online marketing services tailor made to your companies’ requirements.
When employing a marketing agency you should always go off their knowledge along with recommendations (if possible) off other clients. Most web agencies will be happy to allow you to speak to some of their existing clients to get feedback on how they work and the results they have achieved.
Once you have agreed to go with an agency and they have come up with a marketing strategy for you, try and make sure that you stick to it as much as possible. Often clients will say that they want to save a bit of money by doing some of the work themselves. This often does not happen though, and the website then suffers for it. Be honest with yourself and decide if you really have the time or resources to carry out the tasks required by the marketing agency, if not then let them do what they are good at.