Content is King

Search Engines like Google expect the pages in your site to contain useful information and for that copy to contain the main words and phrases potential visitors will use to search for likely sites to visit.

So if you are selling Coffee Widgets your website needs to explain that, it needs also to explain that there are different colours and to state what they are - red coffee widgets, green coffee widgets etc. And if the widgets come in different sizes then also state that in the copy.

Modern Use of Keywords

At one time, stuffing the META Keyword tag with words and phrases to attract the search engine was acceptable, and there are many websites in existence that still use keywords in this way.

Today, search engines prefer to use their technology to deliver "relevant content" in return to a searchers query. They get this content from crawling your web pages and looking at likely terms, words or phrases used in the text on your site.

This site does NOT include any keywords, although the META keyword tag is shown as being present in the HEAD section of the pages.

Where keywords and key-phrases have a modern use is where there are alternative spellings (often because you have written in British English) i.e. color, endeavor, behavior, catalog, center, gray, program, tires etc, etc.

Keyword Tag Placement

If you are going to add Keywords they are located in the HEAD section of your page, replace the words "keyword here" with your keywords and phrases - separated by commas.

By the way, don’t think you can spike the keywords by using the same word repeated over and over, as most search engines have refined their spiders to ignore such spam.