Basically Two Type of SEO Technique
It conforms to the search engine's guidelines.
It does not involve in any deception.
It ensures that the content a search engine indexes, and subsequently ranks, is the same content a user will see.
It ensures that a web page content should have been created for the users and not just for the search engines.
It ensures good quality of the web pages.
It ensures availability of useful content on the web pages.
Black Hat SEO - Black hat SEO is more frequently used by those who are looking for a quick financial return on their Web site, rather than a long-term investment on their Web site. Black hat SEO can possibly result in your Web site being banned from a search engine.These techniques are also known as spamdexing.
Attempting ranking improvements that are disapproved by the search engines and/or involve deception.
Redirecting users from a page that is built for search engines to one that is more human friendly.
Redirecting users to a page that was different from the page the search engine ranked.
Serving one version of a page to search engine spiders/bots and another version to human visitors. This is called Cloaking SEO tactic.
Using hidden or invisible text or with the page background color, using a tiny font size or hiding them within the HTML code such as "no frame" sections.
Repeating keywords in the meta tags, and using keywords that are unrelated to the website content. This is called meta tag stuffing.
Calculated placement of keywords within a page to raise the keyword count, variety, and density of the page. This is called keyword stuffing.
Creating low-quality web pages that contain very little content but are instead stuffed with very similar keywords and phrases. These pages are called Doorway or Gateway Pages.
Mirror websites by hosting multiple websites - all with conceptually similar content but using different URLs.
Creating a rogue copy of a popular website which shows contents similar to the original to a web crawler, but redirects web surfers to unrelated or malicious websites. This is called page hijacking.
