What is a scientific theory that has been changed due to new evidence?

When new evidence is found, the theory is tested against the new evidence, if the theory and new evidence are compatible then the theory is confirmed, if the new evidence and the theory are not compatible, then this indicates the theory is wrong and the theory must be abandoned or modified.

Sometimes a theory will predict that new things (evidence) will be discovered. In such cases when these things are discovered AS PREDICTED, the theory becomes stronger. For instance some of the outer planets were predicted (using orbital and gravitational theory and observation on the orbits of known planets) and they were later discovered close to where they were predicted to be.