Web Design is an area that includes a wide spectrum of service providers such as web designers and web developers who may be individual freelancers or part of small and mid-level digital agencies with niche skill set employees or the bigger high-end design studios with bigger employee count, larger infrastructure and capability to provide expanded services.

The service provider must intuitively understand the needs of the company and offer the necessary solutions to ensure a healthy web presence. You should consider factors such as easy navigation, user-friendly design, flow, SEO friendliness, and other important aspects. Qualifications, experience and designations of web designing services – A long-standing company's reputation is an indicator of its skill and stability. This reputation also means that the company is able to deliver excellent customer service and design work. 

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It also translates into sound design work and reputation for excellent customer service.a This is very important because several start-ups die out leaving an organization flustered when looking for upgrades and maintenance. Any agency with fair amount of experience, client interaction and sound qualifications is worth a try.

The number of employees and the specific roles and skills. Although an agency doesn't have to be large, certain skills are required to fill those roles. Along with highly skilled sales and marketing professionals.