It is different depending upon which source you are referring to but to keep it safe across all platforms then keep it under 50 characters and make your keyword phrase the first thing mentioned in your title tag using a pipe character | or colon : if necessary.
A keyword is a singular word that you want to rank for such as 'hosting'. A keyword phrase is a group of words that you want to rank for such as 'web hosting'. An exact match is 'web hosting', a phrase match is 'web hosting in michigan' where the original phrase 'web hosting' is intact. A broad...
The link wheel application used to be used in the past to boost rankings but has been found out by Google and is of no use anymore. In fact if anyone of the websites in the link wheel are linked to a linking farm it would actually do harm to your rankings.
This used to be a spammy way to share links between three sites to boost rankings in the search engines but since it has been discovered anyone using this technique gets penalized and it has absolutely no value anymore along with meta keyword phrases.
Keyword density is the percentage of how it is mentioned on your web page compared to how many words are on it and is generally not used to determine ranking anymore. If you read the page and it sounds spammy then you can be sure that the search engines will think it is spammy as well and not...