Inlinks

A synonym for back links. Popularized by Yahoo

NoFollow

A tag used to stop search engines parsing on PageRank to sites linked to the host site

Deep Crawl

Deep Crawl
Once a month, Googlebot will crawl all of the links it has listed in it's database on your site. This is known as the Deep Crawl.

PFI

Abbreviation for Pay For Inclusion. Many search engines offer a PFI program to assure frequent spidering / indexing of a site (or page). PFI does not guarantee that a site will be ranked highly (or at all) for a given search term. It just offers webmasters the opportunity to quickly incorporate changes to a site into a search engine's index. This can be useful for experimenting with tweaking a site and judging the resultant effects on the rankings

Reciprocal linking

the practice of trading links between websites

Dead Link

Dead links should always be avoided. In the first place they make your website look sloppy to your visitors and search engines also don’t like them for determining your content and PR. A dead link is basically a hyperlink pointing to a non-existent URL. There are several tools on the internet that can automatically detect your websites dead link. Also, your logs can tell you what pages were not found, so you can determine which pages link to them.
A simple way to solve the problem is to create custom 404 pages that tell users the page could not be found, but does provide links to other pages on your website. This way users will not immediately hit the back button and they’ll stay on your site.
You could do this by directing all non existing pages to your some page using code in a htaccess file: