Here's a list of style changes made for problems 17-26: *17: Bold tags *18: Bold tags *19: ul and li tags for leap year information *20: var tags and line break *21: var tags *22: added code tag *23: var tags *24: centered text and var tag *25: sup tags, tab-like spacing, and CSS grid for spacing *26: sub, sup, and var tags, and CSS grid for spacing BREAKING CHANGE: None