Avoid "one of" unless it's followed by a bulleted list. You can normally leave it out and just use "or". If you cannot leave it out, that might be a good indication you want to use a bulleted list for clarity.
"A hierarchy" (not "an").
Use e.g., and i.e., instead of their non-comma-ending variants.
Casing
"web", unless at the start of a sentence
Punctuation
Spaces around "—" (em dash)
Lowercase after colon ("The slot attribute is used to assign a slot to an element: an element with a slot attribute is assigned to the slot created by the slot element whose name attribute's value matches that slot attribute's value")
WHATWG