When designing forms, make sure there is enough space between fields and the labels. Take into account people who zoom the content. But also avoid having too much space between them.
Ensure that form elements include clearly associated labels.
While it is possible to provide a visually hidden label for form fields, please avoid it. When you provide a visible label, all users benefit.
If you insist on hiding the visual labels, ensure the developer provides some labelling information.
The most logical place for an error message is between the field and its label. It's important to convey the error message to all users.
Consider adding an icon or some other visual indicator for error messages. Color is a good visual way to show an error. But remember to use some other visual cue besides color.