HTML / XML / JS, low-level validity (cross-cutting)HighInferred
Content before <head> / malformed start
What it is
Markup before the head.
Why it matters
Browsers/Google may relocate elements, breaking head directives.
How to fix it
Start the document correctly.
Impact
Medium-high. Inferred.
Evidence
Valid document structure protects head directives. Google Search Central, Robots Meta Tags Specifications