Understanding the Internet and Web Technologies
What is the Internet?
The Internet is a global network of networks, connecting computers worldwide. This connection allows us to access and display web pages through a browser and utilize various online services.
What are Hyperlinks?
Hyperlinks are elements embedded in web pages that provide quick and easy access to content on other websites.
Webmail vs. Mail User Agent
Webmail: Accesses email accounts through a web page.
Mail User Agent: Accesses email accounts through dedicated software.
System Reliability
A system is considered unreliable if it’s prone to problems. Users expect systems to respond safely and reliably, minimizing failures.
What are Digital Certificates?
Digital certificates verify the identity of a user or website.
HTTP and HTTPS
HTTP: Hypertext Transfer Protocol
HTTPS: Hypertext Transfer Protocol Secure (adds security)
HTTP uses port 80, while HTTPS uses port 443.
Servers
A server is a computer running a program that provides services to clients.
Types of Servers
Local Servers: Machines performing server tasks within the same Local Area Network (LAN).
Remote Servers: Located outside the local network.
The whois Command
The whois command provides information about a remote server, including its IP address and location.
Clients vs. Servers
A client is software that connects to a server. A user is any person using a client to connect to a server, such as an FTP server.
What is FTP?
FTP stands for File Transfer Protocol.
FTP User Types
- Anonymous User
- Registered User
FTP File and Directory Permissions
File Permissions: Reading, Writing, Erasing
Directory Permission: Inheritance
What is Mirroring?
Mirroring creates exact copies of a medium (e.g., hard disk). For servers, it ensures website availability by having copies on multiple servers or a backup online.
FTP Clients and Servers
Client Example: SmartFTP
Server Example: Serv-U
Website Content Synchronization
Manual Synchronization: Requires users to compare files and update information via FTP.
Automatic Synchronization: Software automatically compares and updates files (e.g., Dreamweaver).
FTP Server Ports
FTP servers use port 21 for commands.
Active vs. Passive FTP Modes
Active Mode: Client sends requests on port 21 and receives replies from the server on port 20.
Passive Mode: Connection established on port 21, and the server provides a different port for data transfer.
Web Search Options
Internal Search: Searches within a specific website.
External Search: Searches across the entire web.
Computer Requirements for Basic Web Pages
A powerful computer isn’t necessary for creating basic web pages. A text editor and a web browser are sufficient.
What is WYSIWYG?
WYSIWYG (What You See Is What You Get) editors allow users to create web pages visually.
Text Editor Features for Programming
Specialized text editors often feature syntax highlighting, which color-codes the programming language’s code.
Text Editors for Web Development
Not all text editors are suitable for web development. Some include control codes that can interfere with browser interpretation.
Website Home Page (Index)
The home page is often named “index” because it’s the first file browsers look for.
Case Sensitivity in Website Names
Using lowercase and uppercase in website names can cause issues because some operating systems don’t differentiate between them.
Linking to Downloadable Songs
Linking to copyrighted songs for download without permission is illegal. Linking to free or legally downloadable music is acceptable.
JPEG vs. GIF
JPEG: Supports 16 million colors, uses compression (lossy).
GIF: Supports 256 colors, uses compression (lossless).
JPEG is better for photographs, while GIF is better for vector graphics.
Optimizing Image Loading Time
To prevent slow loading times, use thumbnails, limit image size (e.g., 800×600 pixels), and optimize resolution (e.g., no higher than 150 dpi).
What are Codecs?
Codecs are software programs that compress and decompress audio and video data. A single container can typically use only one codec at a time, though it may support multiple different codecs.