There are several common exterior building signage errors that can occur. Here are some examples:

1. Poor visibility: If the signage is not easily visible, it can fail to serve its purpose. This can be due to factors such as poor lighting, small or unclear lettering, or placement in a location that is difficult to see.
2. Inaccurate information: If the signage contains incorrect or outdated information, it can lead to confusion and frustration among those who see it. This can include things like outdated logos, wrong phone numbers, or incorrect addresses.
3. Bad design: If the signage has poor design, it can fail to capture attention or convey a clear message. This can include things like bad color choices, poor contrast, or overly complicated graphics.
4. Inconsistent branding: If the signage does not follow the branding guidelines of the company or organization it represents, it can undermine the overall message and image of the brand.
5. Damage or wear and tear: If the signage is not properly maintained or protected from the elements, it can become damaged or worn over time. This can make the sign difficult to read or unattractive, and can give a negative impression of the business or organization it represents.