Rule: Good <title>-Tag
The <title> tag should contain height weighted keywords for search engines and a good description for site users.
In most search engines and Browser tabs characters after 66 will be stripped off. The <title> tag content should be optimized for a length up to 66 characters.
Rule: Good URL
A good url is a really important part of a good SEO ranking. The following rules should be completly fulfilled.
Length of URL must be less than 1024 characters
The Internet Explorer will be cut off all characters after the 1024 character of the complete URL and will ignore them. This can result in an error while displaying the content of the page. An other reason is that long URL are not easy to remember or to write into the address bar of the browser.
URL should not contain query parameters
Some search engines have trouble with query parameters. Query parameters should be removed and converted into a clean url e.g. with mod rewrite. A clear mod rewrite based uri can also better used for a good keyword placement within the uri.
URL should not contain umlauts
Umlauts are very bad. At first, search engines have some issues with correct interpreting the real characters. The second point is the really low usability for any user because umlauts will be often shown as hex values (e.g. %C3%9C = Ü) depending on different browser versions. These characters are very bad to type or understand by a user.
URL subdirectory path depth should not be greater than 2
The global (logical) directory depth should not be bigger than 2 directories because this will result in a minor weight of the containing pages. Google Pagerank will be decreased with every page depth.
URL should not contain bad characters
The uri path sould not contain umlauts, uppercase and special characters. Good characters are:
a-z, 0-9 - _ /
Bad character within an URL are very bad and mainly an usability issue because it is not easy to type identify them. One Example: some browsers shows within the address bar the en dash or em dash as an single dash and the URL will be broken if an user copy and paste them.
URL should use dashes (-) as word separator
Google and other search engines will interprete the underscore as not given. e.g. keyword_keyword will become in the search engine index as keywordkeyword. The path should be used dash (-) instead of underscores (_).
High grade of good keywords in URL
Stopwords should be removed because they are wasted space. You should use more relevant keywords instead. All important keywords should be placed at the beginning of the URL and all minor important keywords at the end.
The optimal length of a description is between 130 and 160 characters, the maximum are 240 characters. The characters after position 160 will be mostly croped by search engines.
This tag will be shown below the site title in search results. This is not a SEO relevant tag, but a big usability issue.
Google won't use the meta keywords tag, but other search engines and web services does.
A website should contains the meta keywords tag for other services like delicous.com or other bookmarking or recommondation services because they use the given keywords to recommend tags and keywords for this page.
Try to avoid more than 240 characters within the meta keyword tag because most services will ignore a larger meta keyword tag
There should be only real keywords placed within the meta keyword tag. Please never use descriptive words or sentences.
Rule: Valid Doctype
Ever use a valid document type because the browsers render engine will be forced to quirks mode, which is very slow and reduces the usability and increases the page load time on missing doctypes.
Hint: The doctype must be placed at very first in the document. If any other output starts in front of the doctype (e.g. a blank or line break) the doctype will be not interpreted and the browser renders in quirks (compatible) mode!