Monday, December 17, 2007
In today’s age of high-speed internet, the last thing that users want to do is to wait for a website to load even if it is for a few seconds. One of the “musts” for today’s web design is to create a website that loads quickly enough so users don’t leave your site before the whole page is displayed.
To minimize this problem, many sites are designed to preload images in order to speed up page display. JavaScript is the most common way to preload images but it is not the only option available. An alternative to JavaScript is to use the CSS display: none; property. This technique may be more reliable and it requires less complex code. Easy!
Preloading images using JavaScript is a good technique, however, browsers must be JavaScript-enabled and have JavaScript turned on. Without JavaScript, the images won’t preload.
CSS: Our Best Preloading Friend!
CSS offers us a simple and reliable option. By using display: none;, we tell the browser to request an image from the server, but not to display it on the page. The browser just requests the image from the server and caches it for future use.
Common Uses:
- Use in the home page to load images that will be used on the rest of the website
- Cache all the hover images in your site for menus, slide shows, etc.
The CSS Code:
This is a very simple technique. All we need to do is to place the img tags at the beginning, right under the opening body tag and insert CSS style directly within the img tag:
...
</head>
<body>
<!--preloaders-->
<img src="image_1.jpg" style="display:none;" alt=""/>
<img src="image_2.jpg" style="display:none;" alt=""/>
<img src="image_3.jpg" style="display:none;" alt=""/>
<!--end preloaders-->
...
- Very Important: The empty alt tag is important because screen readers will simply ignore the image. You MUST insert the empty alt tag otherwise your website will fail the W3C’s accessibility standards!
- A good idea is to insert comments like in the example above just to separate and locate your rollover images
Summary:
That’s it for this technique! Very simple, almost no code and same results as JavaScript.
Tuesday, December 11, 2007
Sometimes we want to decorate our site with nice looking text but can’t achieve it by just formatting the text to a different font. Why not? Because not all users have the same fonts installed in their systems.
With CSS we can replace a piece of text with an image containing the graphical presentation of the text. These images will only serve the purpose of decorating the page with a fancier font because they don’t carry any value to the content of the page.
How Can We Achieve That?
There are some CSS techniques in which you set the dimensions of the element to the image’s dimensions and define the image to be the element’s background image. Also, to prevent the text from overlaying the image we have to enclose this text in a span tag and hide it in the CSS using display: none;
There is a problem with this technique: If the image cannot be displayed (broken link, corrupted file, etc) nothing will be visible to the user because the only available text is hidden. This is a no-no in today’s accessibility standards!
There’s a very simple way to replace your text with an image file. We will still use our image and text, but this time we are going to place an empty span tag next to the text that we are going to hide. Then we are going to position that image absolutely, causing the image to overlay the text. Let’s get to it!
The Image:
The CSS Code:
h2{
margin-bottom: 40px;
font-size: 14px;
}
h2 #chapter1{
position: absolute;
width: 240px;
height: 46px;
background: url(chapter_1.jpg) no-repeat;
display: block;
margin: 0;
padding: 0;
}
The XHTML Code:
<h2><span id="chapter1"></span>Chapter 1</h2>
- Note that I added 40 pixels of bottom margin to the h2 element in order to push the paragraph down causing it to clear the image. You can experience with this value depending on the height of your image.
Summary:
With this technique the text will always display even if the image doesn’t load. Also, screen readers will ignore the image and read the piece of text under it – this helps your site’s accessibility. Lastly, this is search engine friendly! Images have no value to search engines but because you have text below them, search engines can read that text. This is a technique that I use abundantly throughout my site.
You can also use this technique with links and also add different images for a rollover state!
Examples:
Click here to see an example.
Click to see a link example with rollover image.
