# Search Engine Optimization (SEO)

## Domain
* use a speaking URL
* differanciate between subdomain and subdirectory

## Title
* every page shound have a unique speaking title (60 - 100 characters)

## Keywords
* every page shound have unique keywords
* max. 10 keywords

## Description
* every page shound have a unique description
* max. 255 characters

## Content
* Content matters the most
* Page Title should appear 3% of content length
* add ~ 3 internal links
* use `strong` tag
* do not provide duplicated content
* article should be at least 300 words

## Headings
* Clear structure `H1` -` H6`

## Images
* Alt tag (60 - 70 characters)
* Use a CDN or a subdomain to allow parallal http-requests

## Links
* add meaningful title
* Only add external links if you got a backlink to your site

## Social Media
* Social link rank up your site
* use social snippets [Facebook](https://developers.facebook.com/docs/sharing/best-practices), [Twitter](https://dev.twitter.com/cards/getting-started)

## Sitemap
* provide a `.xml` sitemap

## Errors and access
* provide 403 - Acced denied page
* provide 404 - Page not found page
* add a `robots.txt` file

## HTAccess
* enable GZip
* enable caching

## Performance
* Performance and loading time matters
* only serve concatenated and minified files
* if possible no redirects

## UX
* User friendly site
* clickable links should not be too small

## Mobile
* create a mobile-friendly site (shown in search results)

## Validation and accessibility
* Write valid markup
* use WAI-Aria tags