SEO

HTML Header
Title Tag

Meta Description Tag

Content

Header Tags
Keyword Consistency
Amount of Content
Image Alt Attributes

Links

Backlinks
Top Backlinks
On-Page Links
Broken Links
Friendly URLs

Usability

Device Rendering
Use of Mobile Viewports
Flash used?
iFrames used?
Favicon
Legible Font Sizes
Tap Target Sizing

Performance

Page Speed
Page Size
Number of Objects
Javascript Errors
GZIP Compression
Image Optimization
Minification
Deprecated HTML
Inline Styles

Social 

Facebook Connection
Open Graph Tags
Facebook Pixel
Twitter Connection 

Twitter Cards & Activity
Instagram Connection
YouTube Connection
YouTube Activity
LinkedIn Connection

Indexing

Noindex Tag Test
Noindex Header Test

Robots.txtXML SitemapsAnalyticsSchema.org Structured Data

Security 

Technology List
Server IP Address
DNS Servers
Web server
Charset