world wide web hyperlinks servers/clients browsers html (hypertext markup language)

World Wide Web

• Hyperlinks • Servers/Clients• Browsers• HTML (HyperText Markup Language)

Hyperlinks

• Clicking will take you to another page or site.• Can be attached to text or images.• HTML CODE:<a href=“http://www.google.co.uk>LINK TEXT</a>

<a href=“http://www.google.co.uk><img src=“google.jpg”></a>

<a> are ‘anchors’ text – both the above will link to google.

Servers -- Clients• Web servers hold web pages• Clients ask for pages (by typing their address in a browser)

• Server sends a copy of the page to client(s)– Too many client requests may crash the server

(this is how a ‘denial-of-service’ attack works)

Web server

Client

Client

ClientClient requests page

Server sends pageClient requests page

Client requests page

Server sends pages

Browsers• Display webpages (convert text html code)

HTML (HyperText Markup Language)

Tags describe to the browser what and how to display stuff.Most come in pairs, open <> and close </>

<b> and this will notThis will be bold</b>

This will be bold

Turn on bold mode

and this will not

<b> and this will notThis will be bold</b>

Output this textTurn off bold modeOutput this text

Tag Result

<b> Bold

<i> Italic

<p> Paragraph

<img> Image

<a href=“…”> Hyperlink

URLs(Uniform Resource Locator)

• The address of files on the internet.– Usually web pages (.html, .php, .asp)– Also images (.jpg, .gif, .png etc)– Other files (.pdf, .docx, .zip)

• The address has parts split by the slashes.

http://www.astorcollege.org/images/pdfdocs/Astor_2013_2014.pdf

http:// the protocol (hyper text transfer)

http://

www.astorcollege.org the domain name

http://www.astorcollege.org

/images/pdfdocs/ the path (the folders within the domain)

http://www.astorcollege.org/images/pdfdocs/Astor_2013_2014.pdf

Astor_2013_2014.pdf the file

http://www.astorcollege.org/images/pdfdocs/Astor_2013_2014.pdf