Bit
Electronically, you can think of this as a circuit that has a voltage across it or not. It is either "on" or off. Digitally, this equates to either a "1" or a "0": it is one binary bit of information.

CSS Class
This is a means of applying formatting attributes to a number of HTML structural elements that are identified together. For example, one might design a class that would change the font color to crimson. One could then specify paragraphs, headings or other HTML elements that would have that class.

Encryption
This is basically a secret code. In modern times we have to encode data passing across networks in order to prevent random people listening to the network from intercepting our information. For that reason there are several systems for public key encryption, which allows two systems that have never communicated before to exchange information in an indecipherable code.

Frames
This was a modification to HTML developed in the early Netscape browser that allowed several HTML pages to be displayed simultaneously in a single browser window. It made it possible to scroll through one part of the page even as the other parts remained static. It was quite useful for creating pages that had e.g. a navigation bar in one area, a standard header, a standard footer, and a scrolling content area.

Hexadecimal
The base-16 number system. Counting in hex goes like this: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F, 10, 11, ..., 1F, 20, 21, ...

Octal
The base-8 number system. Counting in octal goes like this: 0, 1, 2, 3, 4, 5, 6, 7, 10, 11, ..., 17, 20, ...

Procedural Markup
This is markup (in any language) that has only to do with the appearance of the page. It gives no information concerning the actual structure of a document. For example, the <font> tag in HTML does nothing but change the appearance of a font, giving no hint of the document structural element that might engender that change.

Router
A router is a computer that possesses multiple IP addresses. It is capable of looking at the IP destination address of packets it receives and forwarding them on toward their destination.

SFTP
Secure File Transfer Protocol. This is a way to transfer files over the Internet using an encrypted connection. In particular, the encryption is handled by SSH, and the result is that the information you transfer (including user name and password) cannot be unencoded and used against you.

SSH
Secure SHell is used to encrypt information in a connection to a remote computer. This prevents packet sniffers from stealing your information from your network connection.

Structural Markup
This is markup (in any language) that gives information about the structure of a document. It may also be associated with a change in appearance, but the key is that it provides information about divisions, titles, sections, paragraphs, or other aspects of the structure of a document. For example, the <h1> tag in HTML usually changes the formatting on the text it contains, but it also provides structural information concerning the level of a heading it describes.

W3C
The World Wide Web Consortium is the standards body for the Web. It is the organization that discusses and develops standards for the web, and oversees implementation of those standards.