Hidden Text
Hidden text is a generally absolute form of Black Hat SEO in which pages are filled with a large amount of text that is the same color as the background, rendering keywords invisible to the human eye but detectable to a search engine Crawler. Multiple Title Tags or HTML comments are alternative hidden text techniques. Hidden text is easily detectable by search engines and will result in Blacklisting or reduced Rank.

Hit
Hit is a somewhat misleading measure of traffic to a web site. One hit is recorded for each file request in a web server’s access log. If a user visits a page with four images, one hit will be recorded for each graphic image file plus another for the page’s HTML file. A better measure of traffic volume is the number of pages/HTML files accessed.

Gateway Page
Also known as a doorway page or jump page, a gateway page is a URL with minimal content designed to rank highly for a specific keyword and redirect visitors to a homepage or designated Landing Page. Some search engines frown on gateway pages as a softer form of Cloaking or Spam. However, gateway pages may be legitimate landing pages designed to measure the success of a promotional campaign, and they are commonly allowed in Paid Listings.

Inbound Links
Also known as back link, backward link, or backlinks, inbound links are all of the links on other websites that direct the users who click on them to your site. Inbound links can significantly improve your site’s search rankings, particularly if they contain Anchor Text keywords relevant to your site and are located on sites with high Page Rank.