Shipped with every version of Microsoft Windows (beginning with the final beta release of Windows 98), Internet Explorer soon became by far the most popular browser on the web.

Version 4 saw the introduction of Dynamic Hyper Text Markup Language (DHTML) support, combining aspects of scripting with Cascading Style Sheet (CSS) technology and thus allowing web developers the option of bringing far greater interactivity to their previously static HTML documents.

The industry was ecstatic; DHTML provided an effective solution to a large number of problems and seemed ready to lead the way into a new era of client-side web development.

Then came the browser wars of the late 1990s which saw intense conflict between Internet Explorer (compared by many to the Galactic Empire in Star Wars) and Netscape Navigator (The Rebel Alliance?) which caused DHTML’s quest for dominance to stall in the face of incompatible cross-browser DOM (Document Object Model) and CSS implementations.

Further hampered by many users’ refusal to upgrade, DHTML became a cutting-edge technology used by only a few developers due to its limited potential audience.

Indeed one might say that the fear of ‘Browser Backwards Compatibility’ issues (a sadly misguided attitude which plagues the web development industry to this day) is at least partly responsible for the eventual demise of DHTML.

Meanwhile, with Internet Explorer and Netscape Navigator unable to standardise parameters, a company called Macromedia quietly released a product called ‘Flash’ which managed to circumvent browser limitations and consequently cornered most of the market previously considered to be DHTML territory thus hammering another nail into the coffin.

Though many may argue that DHTML is alive and well, consider for a moment the fact that Microsoft’s .Net framework has all but made DHTML obsolete.

Whilst the industry’s acceptance of .Net was initially cautious, the system has proved its value during the past few years and is now seen by many (especially since the release of ASP.Net 2.0) as the future of the internet.

As .Net gathers more momentum we are likely to see a new phase in the internet’s evolution with even Flash’s position on the web threatened (especially in the face of its SEO issues) by the creation and expansion of new .Net applications.

So, DHTML is well and truly relegated to the obsolete technology orphanage or the bookshelf of web development nostalgia. Face it; few developers will employ the use of technology which cannot be trusted to function 100% accurately even between Windows platforms when there are other, far more stable alternatives out there.

The fact is that, at least for commercial and application development, DHTML really is dead.

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An accomplished copywriter, Sasch Mayer has been writing content for web and print for well over a decade.
He is currently living in the Republic of Cyprus and working under contract to IceGiant Web Design.

Definitions:

Web Services are defined as programmable application logic that is accessible using standard Internet protocols.

DHTML behaviors are components that encapsulate functionality on a page. DHTML behaviors are available in IE5.5 and above. To be able to use the behavior in a Web Page in IE5.5, you will need to download the WebService.htc behavior file and save it in the same folder as your html page. The file can be downloaded from the following location: http://msdn.microsoft.com/downloads/samples/internet
/behaviors/library/webservice/webservice.htc

Program Details

Let’s delve into the details of our program.

Step 1: Create the Web Service

Create the file that exposes our Web Service function using your favorite text editor or Visual Studio.Net. Shown below is the code for the Web Service.

<%@ WebService Language="C#" class="TestWS" %>
using System;
using System.Web.Services;
using System.Web.Mail;

[WebService] public class TestWS : System.Web.Services.WebService
{
[WebMethod] public int Add(int num1, int num2)
{
return num1 + num2;
}
}

Code Listing: Save as TestWS.asmx

The web service “TestWS” is very simple – it exposes only one function “Add” which accepts 2 integers as input and returns their sum as the output.

Step2 : Create the HTML Client

First we specify the web service behavior in the html file as follows
<div id="service" style="behavior:url(webservice.htc)" onresult="onWSresult()">
</div>
The id specified for this element to reference the element in script.

Next we map the web service URL to a user-friendly name (“Calculator” in this case).
We add this code in the OnLoad handler for the page to ensure that the web service is mapped before any methods are invoked on the web service.

service.useService('http://localhost/site/code/testws.asmx?WSDL','Calculator');

Now that the webservice is setup for access, we invoke the web service methods asynchronously in two steps. The advantage of asynchronous invocation is that the web page does not have to keep waiting for the web service to return. In the first step, the web method is invoked. A call back function is specified and when the web service completes execution, the callback function gets executed. As a second step, the call back function (or an “onresult” event, if no callback function is specified) gets fired when the web service returns after execution or a timeout error occurs.

The code to actually invoke the Web Service’s web method is shown below. The web method is invoked when the “Add Numbers” button is clicked.

The input parameters to the callService method are “methodname” and the input parameters expected by the web service.

function ExecuteWS()
{

iCallID = service.Calculator.callService("Add",num1.value,num2.value);
}

Our onresult event handler checks the error property to find out if any error occurred in the execution. In case of error, the function displays the details of the error and if successful, the function displays the result from the web service.

The onresult function implementation is shown below.

function onWSresult()
{
if((event.result.error)&&(iCallID==event.result.id))
{
var xfaultcode = event.result.errorDetail.code;
var xfaultstring = event.result.errorDetail.string;
var xfaultsoap = event.result.errorDetail.raw;
document.writeln("ERROR. Method call failed!");
document.writeln("Call ID:" + iCallID);
document.writeln("Fault Code:" + xfaultcode);
document.writeln("Fault String:" + xfaultstring);
document.writeln("SOAP Data:" + xfaultsoap);
}
else if(event.result.error == false)
{
sum.value= event.result.value;
}
}

Here is the complete code listing for the client.

<SCRIPT language="JavaScript">
var iCallID;

Number : <input type="text" name='num1'">
Number : </td> <td><input type="text" name='num2'">
Total:<input type="text" name='sum'">
<button OnClick="ExecuteWS()">Add Numbers</button>
</body>

Code Listing: Save as test.htm (in a folder containing webservice.htc)

Step 3: Test

Here are the results of our program:

Input screen:

If you entered an incorrect integer, for example “xyz” for one of the inputs, the resultant error would be displayed.

Conclusion:

This program provides trivial functionality in terms of application processing logic, but it demonstrates a design architecture to access the vast resources and functionality of the .Net Framework. Imagine the possibilities – you could have simple HTML pages invoking complex, shareable logic through simple internet protocols – the client HTML page does not need to be programmed using the .Net framework.

Dipal Choksi is a Bachelor of Engineering (Computer Science). She has industry experience in team-effort projects and also as an individual contributor. She has worked on Visual Basic, Visual C++, Java, Directory Services, ASP projects

Unlike CGI scripts, JavaScript can be placed directly into your HTML code. It can also reside on your server and be called from a small code within your web page.

This powerful scripting language can be used to create special effects on your web page such as link effects, mouseovers, image roll overs, navigational systems and much more.

Here are a few great scripts to get you started:

Navigation Bar

This script is actually a combination of JavaScript and HTML better known as DHTML. It will enable you to have a mouseover navigational menu at the top of your web page. When you place your mouse over the main menu, a drop down menu will appear. As you move your mouse over the drop down menu, each selection is highlighted. This navigation menu is very similar to the menu used at Microsoft.com.

http://www.brainjar.com/dhtml/navbar/index.html

Dynamic Splash Screen

If you’ve ever wanted to set up a splash screen for your web page, Dynamic Splash Screen will do just that. Splash pages can be used to tell your visitors a little bit about your site or whatever you’d like. The great thing about this script is that it is constructed using a single page. Once the splash messages have been completed, the script will navigate to the URL of your choice. It also includes a link on the splash page that says, “Skip Intro.” Nice effect.

http://www.dynamicdrive.com/dynamicindex3/dynamicsplash.htm

Pausing Up and Down Menu Scroller

This nice little script will enable you to have linked text that scrolls upwards and will pause between each message. You can choose to include a background image and customize the background color and box size. This script provides a nice way to announce new additions to your site or whatever you’d like.

http://www.dynamicdrive.com/dynamicindex2/crosstick.htm

overLIB

Create mouseover popup boxes for your text links. This great script can be used to include information about the links, tips or whatever you’d like. It can create simple mouseover popup boxes or can even create a popup box that will stay open until the user wants to close it. The boxes can also be displayed with or without a caption and colors can be customized. This is a great little script.

http://www.bosrup.com/web/overlib/

Source Protector

Although this script won’t completely protect your page content, it will deter those wanting to steal your code. When you right click on your mouse, an alert box will appear. You can include a message of your choice.

http://www.javascript-page.com/noclk.html

Right Click Menu

This nifty little script not only helps prevent your code from being stolen, but it also creates a pop up navigation menu. When you right click on your mouse, instead of the browser menu appearing, your menu will appear. This little menu can contain live links to other pages on your web site.

http://www.geocities.com/html_4u/rc_menu.html

Banner Rotator

This simple little script will enable you to rotate banners on your web page. You simply add your banner information to the code and place this script within your web page where you’d like your banners to display. Each time your page loads, a new banner will be displayed. Great little script.

http://www.javascript-page.com/banrot.html

Daily Tip

This script will enable you to display a daily tip on your web site. You can program it with tips for the entire month and they will automatically display each day.

http://www.geocities.com/html_4u/dailytip.html

FairWell Window Launcher

Although popup windows can be irritating, this script is a little different. It will launch a new window when your visitor leaves your site. What’s great about this script is that it will only appear the first time someone visits your web site. If you offer your visitors a free publication, try placing your subscription information within this new window. This provides a great way to increase subscriptions to your publication.

http://wsabstract.com/script/cut65.shtml

Locating JavaScripts: http://javascript.internet.com/

Locating DHTML Scripts: http://www.dynamicdrive.com/

Learn more about JavaScript: JavaScript Learning Center http://www.javascriptmall.com/learn/contents.htm

Although JavaScript can certainly help you spice up your web site, there are many scripts that your visitors may find irritating. Try to avoid scripts such as mouse trailers, mouseover sounds, mouseover pop up windows and mouseover redirects. Carefully select scripts that will enhance your visitors experience and encourage them to return in the future.

Copyright 2000 All rights reserved

Shelley Lowery is the author of the acclaimed web design
course, Web Design Mastery. http://www.webdesignmastery.com
An in-depth guide to professional web site design. Visit
Web-Source.net to sign up for a complimentary subscription
to Etips and receive a copy of the acclaimed ebook, “Killer
Internet Marketing Strategies.” http://www.web-source.net

The essence of the term stands for almost any coding that creates movement or interactivity by employing the standards of the 4.0 level Netscape and MSIE browsers.

But there was movement before with animation and interactivity with forms…

Yeah, see… that’s the rub. For something to be considered DHTML it has to employ version 4.0 browsers. Again, an argument I’ve heard is that DHTML is only viable if it occurs within the Explorer 4.0 browser. I’ve heard DHTML discussed as being PowerPoint for the Web.

On the other hand, some people have stated that DHTML includes Netscape’s Layering Commands.

The best description I can offer is that DHTML is any combination of Style Sheets, JavaScript, Layering, Positioning, and Page Division at the 4.0 browser level, intended to create movement or user interactivity…

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