Search Engine Optimisation (SEO) should at all times be carried out in an ethical way so that the Search Engine Placement of the client website will be on the initial page of a set of organic search engine results. These results will normally come after a list of sponsored sites that are relevant to the search keyword(s) typed in.

The procedure by which a search engine, e.g. Google, decides which web sites are relevant to the keyword(s) submitted for search, is by having earlier indexed the pages and filed the results in a database. Thus by searching the index for the keyword(s) a fast response is assured, typically in the order of under a second.
The search engines use a program to compile the database, known as a robot or spider, and these robots have been engineered and refined to make out unethical practices that they find on web pages, which they could well then eliminate from the index. In some cases the web site may be excluded as a whole.

The robot values the web pages by several means: The number of times a keyword is found on a page, and the number of times independent sites link to the page.

For clients operating Online Marketing services, it is important that their web sites are long running as they may well support many other clients.

Keywords:
Unethical Practice:
Keyword Stuffing is an unethical exercise of using a keyword lots of times in a web page, usually by using text that is the same colour as the backdrop so that it will not be viewed by a user but will be seen by the robot.
This can also be used for keywords in Meta tags in the html head of the web page coding.
Ethical Practice:
Ethical exercises focus on what the user experience will be, so the page wording should be appropriate to the page title and the page title should mirror the link that was used to reach it, as well as the actual content. Content should be carefully written in good English with no spelling or grammatical errors, and should highlight the product or service that the page is concerning. Keywords should be part of the usual flow of text and repeated simply as often as reasonable reading allows. For keywords in Meta tags a exclusive list of keywords should be used.

Links to the page:
Unethical Practice:
An unethical optimizer may create what are known as Doorway Pages, where the text is probably just keyword stuffing and a link to the promoted web site.
Ethical Practice:
The ethical system is to create useful pages that can be made sense of by a user and have links to the client site.

If looking for a Search Engine Optimisation Company, ascertain which methods they use before committing yourself to their services.