I heard somewhere that clocking and doorway pages are blackhat seo technique and i had read more about it but i did get it so please tell me about those.
Cloaking is the process of providing the search engine with one set of HTML code while offering an Internet visitor another. The Internet visitor gets a normal web page while the search engine gets a highly optimized one.
Doorway pages (cookie-cutter pages) are additional landing pages (splash pages) that are slightly varied one from the other according to keyphrases and are intended to capture targeted traffic according to specific keyphrases. A web site should only have one landing page and in SEO, the landing page should clearly offer the search engine and the Internet visitor any primary keyphrases. Secondary and auxilliary keyphrases can be introduced in sub-level pages.
The Doorway pages are a type of web page shaped to gain fame with a definite search engine. They are referred to as bridges, gateways, and entry pages. They are a substance of disputation inside the search-engine optimization world.