If you want to analyze the existing keywords on a specific webpage, or if you want to research the keywords that should be on your page to rank for a specific term, then check out these tools.
Example.com Keyword Density Checker
The Example.com Keyword Density Checker tool extracts keywords from a website and determines how often they occur. Get a list of one-word, two-word, and three-word keyphrases organized by keyword density. Check the keyword density of a site to see how search engines view your content.
Example.com Keyword Extractor
Extract keywords from any website and create a list of single, double, and triple word keyphrases using the Example.com Keyword Extractor.