Out of date styling
If your website looks like it was made in the 1990s (a lack of structure or use of more than 3 colours could be a tell-tale sign of this), then perhaps you could benefit from revising the design. If things look like they haven’t been updated in a while, what message will that send to your users? After all, a website is your shop window to the world.
Tip: Take a look at competitors’ websites. What are they doing well? Are there any websites outside of your industry that you like the look of? Could they offer some guidance with regards to style?