Headings that skip a level
This page goes from an H1 straight to an H4, as if H2 and H3 did not exist.
The first section, which should have been an H2
Headings are not just larger and smaller text. They form a nested outline that screen readers announce and that search engines use to understand structure. When the page jumps from H1 to H4, a screen reader user hears that they have gone three levels deep with nothing in between, which is confusing and makes the page harder to move through by headings.
Another skipped-level section
The fix is about the tag, not the size. If you want smaller text, use CSS, but keep the heading one level below its parent. A clean outline goes H1, then H2, then H3, then H4, so anyone reading the structure can follow it without a missing rung.