What goes wrong.
THE SITE IS NOT INDEXED
The visibility setting, or robots.txt.
PAGES ARE DUPLICATED
www and non-www both resolving, or parameters creating variations.
URLS CHANGED WITHOUT REDIRECTS
Every old address broken, every link lost.
THE SITEMAP IS WRONG
Listing pages that do not exist or should not be indexed.
MIXED CONTENT WARNINGS
Insecure resources on a secure page.
SLOW PAGES
Images and no caching, usually.
CONTENT HIDDEN ON MOBILE
May not be considered at all.
BLOCKED CSS AND JAVASCRIPT
Prevents proper rendering.
REDIRECT CHAINS
Value lost through each hop.
THIN PAGES
Tag pages, empty categories, near-duplicate location pages.
STRUCTURED DATA ERRORS
Invalid markup, or markup not matching the page.
WHAT TO CHECK MONTHLY
Search Console. It reports most of these.
