Your users rely on your website to get things done. They are used to doing it a certain way. So when things change, people get frustrated. Nevertheless, change is necessary. So the job of your web design and development team is to try to make the changes go over as smoothly as possible.
Communicate with Your Users
Testing is a valuable tool to help you figure out where the problem areas of your website are. Gathering information by polling or asking your users to give their feedback can be incredibly valuable. But, keep in mind that sometimes what a user tells you about their experience with your site may not exactly match what really happens when they are actually on the site. There may be inconsistencies with a users intent and their action because of the contextual factors involved. Every time someone uses your site, the situation is different and therefore the results are different. Monitoring and using things like Google Analytics metrics will give you facts to compare to your collected empirical data.
Types of Change
Design changes are more immediately noticed, while workflow changes may take time to be detected by your users. Dissatisfaction with design changes may not be enough to keep them from using the site, but if the functionality of the site is compromised users may be discouraged. Therefore it is vital to ensure that any workflow changes will benefit the user in the end. Workflow changes can bring short term user dissatisfaction but valuable long term gain. Ultimately people are able to learn and adapt to the changes within a few days, and as long as the benefits last longer than this relearning period, their experience will ultimately be positive.
When is change necessary?
Change is always necessary when it solves a problem or serves a specific purpose. Ease of use, being the ultimate goal. Increased and varied functionality is only valuable when truly needed. You also need to consider the types of users you are designing for. There is no need to hold back for a small portion of your users, while inhibiting the experience of most of your users. Maintaining core consistencies with your old site, such as keeping things in the same general location and using familiar visual cues, will assist your user with making a smooth transition to your new design.