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- Web Palette
The palette consists of 216 colours which will display accurately on both Mac and PC platforms without dithering.
Top - WebTV
WebTV uses a restricted screen size of 544x378 pixels. Although this is close to the old VGA monitor resolution of 600x400, most computers are running at 600x800 or higher. Some WebTV browsers are unable to scroll horizontally, only vertically. This leads to page content being cropped from the right side of the page. Other considerations include inverting text colours to light on dark (negative display) instead of dark on light (paper/monitor display) and avoiding any elements less than 2 pixels in width or text sizes less than about 10point. This represents a considerable restriction on certain web pages and although WebTV has tiny overall browser usage, it is experiencing slow growth, e.g. in hotel chains.
Top - White Space
The default behaviour in HTML is to compress all consecutive white space (tabs, spaces and newlines) as one single space. The
<pre>tag allows each space to be shown in a monospace (typewriter type) font. The white-space attribute allows the same<pre>type behaviour to be controlled via CSS and with any font available. Browser support forwhite-space:preappears patchy.style="white-space:pre;"- display all white - space .
style="white-space:nowrap;"- prevent line-breaks without a <br> tag.style="white-space:normal;"
Top - Width
Sets the visible width of an image or object. Objects larger than the set width may be shown with scrollbars, depending on the exact nature of the data. Images are reduced to the set size by the browser. This usually results in dithering and is best avoided by reducing the size of the graphic to match the size required for the site before uploading to the website.
Top - Window
Javascript
- PropertiesWhether a window has been closed:
var closed = window.closed();
The default status line text:
var text = window.defaultStatus;
List of frames within a window:
window.frames[];
Number of frames within a window:
window.length;
History.
Location of the window:
var locate = window.location;
Name of a window:
var name = window.name;
Navigator
Window that opened this one:
var window = window.opener;
Parent of this frame:
var parent = window.parent;
This window:
window.self;
Change the status line temporarily:
window.status = "new message";
- MethodsDisplay an alert box:
window.alert("message");
Display a confirm box (yes or no answer):
window.confirm();
Display a prompt box to get string input:
window.prompt("Enter a string:","here");
Give keyboard focus to a window:
window.focus();
Remove keyboard focus from a window:
window.blur();
Set a timeout (postpone an event). To repeat execution, call setTimeout() from within the calling function, see the CodeHelp main site:
//first define a function, e.g. drop()Cancel a deferred event (see timeout):
var timeID = setTimeout(drop(),10);
window.clearTimeout(timeID);Open a new window (if a window with the same name is already open, focus() is called for that window):
open(url,name,features,replace);
e.g.
window.open("file.html","Remote",'width=500,height=350,scrollbars,toolbar,resizeable,menubar');
To omit scrollbars etc. from the new window, omit the relevant feature from the list.
Close a window:
window.close(); - Event HandlersEvent handlers for the window can be set within the
<body>tag.
<body onLoad="load_func();">
<body onUnload="unload_func();">
<body onblur="blur_func();">
<body onfocus="focus_func();">
- Properties
- WML
WML is a standard vocabulary of XML - the DTD is pre-defined by the WAPForum and all WML documents must match the same DOCTYPE. Make sure that you use only WML tags in WML documents, if you make a mistake, the underlying XML will not be well formed and the WML document will be invalid. Unlike HTML, WAP Gateways will not load an invalid document and because mobile phones do not have the error checking capability of IE5 there will be no browser error given either. The user may just get a blank screen or a cryptic WAP Gateway error message. You must validate ALL your WML documents before uploading them to a website, using a variety of tools. The quickest and most helpful initial check is in an XML editor, which can report errors of structure, like Microsoft XML Notepad.
You can view the WML tutorial at CodeHelp site in XML using any XSLT compatible browser by following this link: CodeHelp WML for XSLT supporting browsers. This section also includes details of microbrowsers, WAP Toolkits that you can use to test your WML code and a page that allows you to add your own WML site to the CodeHelp searchable links. (Links can also be added over a WAP connection at the site below.
Other browsers can view a HTML version of the WML tutorial.
CodeHelp also has a native WML site - accessible only to WAP phones or microbrowsers like WinWAP or a WAP Toolkit. The WML site provides access to email via the WAP phone (not as convenient as it may sound) as well as a search engine for WML sites. The URL to enter into your WAP device is www.codehelp.co.uk/wap/index.wml.
Top - Wrap
Caution: The wrap attribute does not exist in the W3C HTML4 standard. It is not deprecated, it was never officially recognised. The standard makes it clear that the function of the wrap attribute should be part of the behaviour of the
User agent
(browser) and not left to the website. When describing the use of cols in textareas, the standard only says:
Users should be able to enter longer lines than this, [the number of cols defined] so user agents should provide some means to scroll through the contents of the control when the contents extend beyond the visible area. User agents may wrap visible text lines to keep long lines visible without the need for scrolling.
See also input tags (textareas). The wrap attribute was used in HTML3 to dictate how the control handles text extending beyond the width of the control. Virtual or soft allowed the text to wrap to the size of the control on the user's display. Physical or hard required the user to enter the end of the line manually. These line ends were transmitted as part of the form content. Off was the default setting - the lines did not wrap within the control but line ends were not transmitted. Virtual was usually the most useful.
Top - XML
HTML is the foundation of the WWW and is perfect for presenting a multitude of web pages. Problems arise when large sites need a consistent look and feel with variable content. Creating 30 almost identical HTML files can be straightforward - maintaining each one and making sure that changes in one are reflected in all others is the most laborious and error-prone problem of web site design.
Enter XML. CSS began the process of separating the data (HTML) from the presentation (CSS) and the use of external CSS files common to a range of HTML files greatly improved the situation. However, this still left changes to the HTML meaning changes to every single file. XML continues the separation of data from presentation, to the point that one XML stylesheet contains all the common HTML code and a separate CSS stylesheet contains the formatting code. The XML file itself only needs to contain the code that is specific to that page.
The CodeHelp XML site uses XML to remove the need to duplicate the basic HTML structure of the page. This HTML code is held in the XML stylesheet - one file that is used to create all other XML files that are linked to it. One file to update, one file to check. The larger the site, the greater the benefits of XML. Each page is then constructed from the stylesheet with only the customised data loaded from the XML file. Custom written tags provide total control over where and how the data is included. The XML files used in CodeHelp contain only 20 or so tags. All the rest of the code - backgrounds, main index page links, positioning code, mailto links, other common images, all are constructed on the fly from the spreadsheet. Processing time is reduced because each file uses the same file from the browser cache instead of downloading another 12kb of repeated data.
You can view the CodeHelp site in XML using any XSLT compatible browser by following this link: CodeHelp for XSLT supporting browsers.
Other browsers can view a HTML version of the XML tutorial.
Top - Z Index
CSS allows absolute and relative positioning of elements and Javascript further allows for dynamic changes to those positions after the page has loaded. It is therefore inevitable that some method is required to handle occassions when two separate elements are required to overlap. This is the Z Index - after the Z axis that converts a two dimensional x-y graph into a 3D x-y-z shape. A high value of Z places the element closer to the viewer and therefore obscures an element with a lower value of Z occupying the same x-y location. (x = left, y = top). If the blue panel covers part of the red panel, your browser would appear to be ignoring the z-index attribute - it works in Mozilla.
AB
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