Favicon
The small icon you often see next to URLs in a web browser.

Feed
Wikipedia describes feed as: a web feed (or news feed) is a data format used for providing users with frequently updated content. Content distributors syndicate a web feed, thereby allowing users to subscribe to it. Making a collection of web feeds accessible in one spot is known as aggregation, which is performed by an Internet aggregator. A web feed is also sometimes referred to as a syndicated feed.

Feed Reader
Software or web application which aggregates syndicated material such as news headlines, blogs, podcasts in a single location for easy viewing.

FFA (Free For All)
Free for all pages are sites which allow anyone to add a link to them. They have no value to users and are ignored or penalized by the search engines because the outgoing links go to unrelated and low quality websites.

Flash 
A vector graphics-based animation software which allows a web designer to embed interactive multimedia into web pages. Search engines struggle to index and rank flash websites because flash typically contains so little relevant content.

Flash Intro 
Those annoying animated 'shorts' you sometimes have to sit through upon opening a site.

Fresh Content
Fresh content does not mean re-editing old content. It more often refers to creating new content. The primary advantage of fresh content is search engines love it. But keeping a website dynamic with fresh content ensures people will revisit your site.

Frames
Separate web pages are combined into one, each potentially with its own scrollbar.
Frames are bad for SEO because spiders can fail to correctly navigate them.
Users don’t like them because it’s difficult to bookmark framed sites.

FTP (File Transfer Protocol)
FTP is used to transfer data from one computer to another over the Internet, or through a network.

Fuzzy Search
Search which will find matching terms when terms are misspelled (or fuzzy).
Fuzzy search technology is similar to stemming technology, with the exception that fuzzy search corrects the misspellings at the users end and stemming searches for other versions of the same core word within the index.