There are three safety levels of found registry errors. They have different icons displayed - green, yellow and red.
Entries are safe to correct with default suggested correction.
Modifying these entries without reviewing may cause problems. Please check suggested corrections.
Modify these entries only if you are sure how to correct them. Note that really unsafe entries are in the excluded lists and never displayed.
Yellow and red flags do not mean critical errors. They only mean that user should carefully check all automatically suggested corrections for those invalid entries. This is for advanced users. Other users knowing a little about the Windows registry may simply leave yellow and red entries without changes. By default such entries are not selected for corrections - no selection marks in the related checkboxes.