What is DHTML
lDHTML is the art of making HTML pages
dynamic!
lDHTML is a combination of technologies used
to create dynamic and interactive Web sites.
lTo most people DHTML means a combination of HTML, Style Sheets and
JavaScript.
Features
lChanging the tags and
properties
lReal-time positioning
lDynamic fonts (Netscape
Communicator)
lData binding (Internet
Explorer)
Changing the tags and properties
lThis is one of the most common
uses of DHTML. It allows you to change the qualities of an HTML tag depending
on an event outside of the browser (such as a mouse click, time, or date, and
so on). You can use this to preload information onto a page, and not display it
unless the reader clicks on a specific link.
Real-time postioning
lWhen most people think of DHTML
this is what they expect. Objects, images, and text moving around the Web page.
This can allow you to play interactive games with your readers or animate
portions of your screen.
Dynamic Fonts
lThis is a Netscape only
feature. Netscape developed this to get around the problem designers had with
not knowing what fonts would be on a reader's system. With dynamic fonts, the
fonts are encoded and downloaded with the page, so that the page always looks
how the designer intended it to.
Data binding
lThis is an IE only feature.
Microsoft developed this to allow easier access to databases from Web sites. It
is very similar to using a CGI to access a database, but uses an ActiveX
control to function. This feature is very advanced and difficult to use for the
beginning DHTML writer.
Advantages of DHTML
l1. Fast and Zippy: - dHTML
loads content on fly. Your whole page does not loads but only the content part
that needs to be altered, so saving the crucial time for the users and giving
the snazzy look to the website.
l2. Plug-ins, we don’t need
them:- dHTML uses most of the features already present in the browsers, so
there is no need to download any sort of Plug-ins.
Advantages of DHTML
l3. Great Utility:- The dynamic
features possessed by dHTML are helping web designers to create Web pages that
posses compact looks, downloads fast, have graphic effects, provides greater
functionality and can hold much more text or content all at the same time.
Disadvantages
lUses script languages which
mean
–All
variables are variants
–Error
handling is limited
lDebugging can be awkward
lCostly Editing tools: -
although dHTML provides great functionality but the editors’ available for that
in market are pretty expensive. Examples of dHTML editors are Dreamweaver and
Fusion.
lLong and Complex coding: -
dHTML coding is long and complex. Only the expert Javascript and HTML
programmers can write them and edit them with good degree of functionality.
lBrowser Support problems: -
dHTML suffers from browser support problems for different browsers. For
example, a code written for Netscape might not work in Internet Explorer and
Vice-Versa. The problem arises due to the different features of browsers.
What is HTML?
4Telling
the browser what to do, and what props to use.
4A
serises of tags that are integrated into a text document.
Tags are ;
4
surrounded with angle brackets like this
* <B> or <I>.
4Most
tags come in pairs
* exceptions: <P>,
<br>, <li> tags …
4The
first tag turns the action on, and the
second turns it off.
4The
second tag(off switch) starts with a
forward slash.
* For example ,<B> text
</B>
4can
embedded, for instance, to do this:
* <HEAD><TITLE>
Your text </HEAD></TITLE> it won't work.
* The correct order is
<HEAD><TITLE> Your text </TITLE></HEAD>
4not
case sensitivity.
4Many
tags have attributes.
* For example, <P ALIGN=CENTER> centers
the paragraph following it.
4Some
browsers don't support the some tags and some attributes.
Structure of HTML
•HTML documents are structured
into two parts, the
•The head contains information
about the document
that is not
generally displayed with the document,
such as its TITLE.
•The BODY
contains the body of the text, and is
where you place
the document material to be
displayed.
Elements allowed inside the HEAD,
Basic HTML Document Format
How to Create and
View an HTML document?
1.Use an text editor such as Editpad to write the document.
2.Save the file as filename.html on a PC. This is called the
Document Source.
3.Open Netscape (or any browser) Off-Line
4.Switch to Netscape
5.Click on File, Open File and select the filename.html
document that you just created.
6.Your HTML page should now appear just like any other Web
page in Netscape.
7.You may now switch back and forth between the Source and
the HTML Document
lswitch to
Notepad with the Document Source
lmake changes
lsave the
document again
lswitch back
to Netscape
lclick on
RELOAD and view the new HTML Document
lswitch to
Notepad with the Document Source......
HTML Disadvantages
•Page
numbers corresponding to the
print are often not
present
•May
require multiple files
•May
require on-line access
HTML Advantages
•Widely
available
•Supports
navigation by heading if properly tagged
•Works
with a wide range of AT
•Known
Web surfing concepts apply
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