Random Content Rotation Made Easy

Key Takeaways

The script presented in this post allows for the creation of random rotation of any (X)HTML code, making a webpage appear fresh and dynamic to repeat visitors.
The script is server-based and not dependent on JavaScript. It creates a style sheet that sets all but one random
to display: none. This keeps the content accessible to search engines and screen readers.
The script is written in Perl and can be used on nearly all web hosts. The only line that may need to be changed is the first line of the script, which points to the Perl executable on your server.
The script can be customized to suit different needs. For instance, instead of using display: none, the CSS can be changed to absolutely position the content off the visible screen area, making non-random content more accessible to screen readers.

After reading Random Image Rotation by Dan Benjamin, I thought I’d share a method I used recently to rotate ‘Success Stories’ on my site. The concepts and script I will present in this article can be used in the same way as Dan’s to keep a page from becoming dull to repeat visitors.

The concept is similar but not the same; the script we’ll talk about here can be used to create random rotation of any (X)HTML code you choose. It’s server-based and not dependent on JavaScript.

Overview

You create a number of <div>s. You import a style sheet generated by a Perl script. The style sheet sets all but one random <div> to display:none. Your design looks fresh, search engines pick up all the content (so, any links in the random content are seen every time), and screen reader users get it all too*, keeping your content accessible. The script is simple, but useful.

*As pointed out by Joe Clark, some screen readers respect display:none, so this does not apply to those delinquents. You can use something other than display:none if you wish.

Installing the Script

The script is written in Perl and should be usable on nearly all Web hosts — you can download it here. Refer to your Web host’s support desk or help files if you don’t know how to get this script working. The only line you may need to change is the first line of the script, which points to the Perl executable on your server.

The Example

As an example, we’ll use 3 ‘Success Stories’; each contains a page of content:

success1.html 

success2.html 

success3.html

We have room to point to only one of these Success Stories at a time when we display our homepage page to a visual browser, but there’s no reason why screen readers and search engines shouldn’t see all three every time.

Let’s create three sections of code that can be used to lead users from the homepage to the full Success Story content pages:

<div id="success1" class="success-story"> 

  <p><a href="/success1.html"><img src="/images/success1.jpg" alt="Foo Ltd." border="0" />Foo Ltd. has been invaluable in bringing our product to market successfully.....</a></p> 

</div> 

 

<div id="success2" class="success-story"> 

  <p><a href="/success2.html"><img src="/images/success2.jpg" alt="Foo Ltd." border="0" />Foo Ltd. delivered a highly professional service.....</a></p> 

</div> 

 

<div id="success3" class="success-story"> 

  <p><a href="/success3.html"><img src="/images/success3.jpg" alt="Foo Ltd." border="0" />Foo Ltd. provided the project management skills we were looking for.....</a></p> 

</div>

The code has a <div> for each section of content that we want to include in the rotation. The content of the <div>s is not important to the script, however. The important part is the id of each <div>, which has two sections: a prefix and a number. The class of the <div> can be whatever you need for CSS display purposes. You can, of course, use the id, but if you do this, you’ll have each id appearing in your selector. Using one class makes this easier.

The Prefix

The first part of the id is the prefix. The prefix comprises everything that comes before the number. In this example, the prefix is:

success

We will pass this prefix to the script.

The Number

The second part of the id is the number; ids must always start at 1 and ascend in increments of 1 (1,2,3 etc.). You can have as many ids as you like.

We will pass the highest number to the script.

The Script

The concept behind the script is simple. The script generates a style sheet that will hide all but one (random) <div> using display:none. We add it to our homepage using the standard <link> element:

<link type="text/css" rel="stylesheet" href="/cgi-bin/random_content.pl?t=3&p=success" />

The important part here is the href that points to the style sheet:

/cgi-bin/random_content.pl?t=3&p=success

Let’s break it up and look at each section in turn.

/cgi-bin/random_content.pl?

This section identifies the location of the script on your server, followed by a question mark.

t=3

t stands for total. You should replace 3#ec#/ with the total number of content <div>s you used above.

You need the ampersand to separate the two values you’re passing.

p=success

p stands for prefix. You should replace success with the prefix you used for the ids of your divs.

That's it! Visitors that don't make use of the CSS, such as search engine crawlers and screen readers that ignore CSS, will get all the content every time. With a little imagination, there are many interesting things you can do with this simple script. It worked very nicely for me; I hope it does for you, too!

Changing The CSS

As I mentioned earlier, you don't have to use display:none -- you can change it if you wish. One alternative is to absolutely position the content so that it lies off the visible screen area, say, 1000 pixels to the left. To do this, you'd change the following line:

my $css = '{display:none;}';

Change it to:

my $css = '{position:absolute; left:-1000px; top:0px;}';

This should make non-random content more accessible to screen readers. The choice is yours!

A Parting Comment

Thanks to the brilliance of Internet Explorer, you may have problems if you try to view the output of this script directly in your browser. Problems arise because the browser doesn’t listen to the MIME type that the script outputs when you try to view it directly (though it works fine when it imports it as a style sheet).

If you want to view the output using this browser, you will need to add &debug=1 to the URL you use to access the script. This causes the script to output using a MIME type of text/plain instead of text/css. Don’t use debug=1 when importing as a style sheet; only add it if you experience problems viewing the output of the script in your browser for testing purposes.

The other alternative is to rename the script “.css”, which should also fix this problem without you needing to add debug=1, as this tricks the browser into believing it’s getting css.

Frequently Asked Questions about Random Content Rotation

How can I rotate an image by a random amount using CSS?

Rotating an image by a random amount using CSS involves using the transform property. The transform property applies a 2D or 3D transformation to an element. This property allows you to rotate, scale, move, skew, etc., elements. To rotate an image, you can use the rotate() function. The rotate() function rotates an element clockwise or counterclockwise according to a given degree. For example, to rotate an image by 30 degrees, you would use the following code:

img {
transform: rotate(30deg);
}
To rotate an image by a random amount, you would need to use JavaScript to generate a random number and apply that as the degree of rotation.

How can I rotate an image with JavaScript?

Rotating an image with JavaScript can be achieved by manipulating the style property of the image element. The style property is used to get as well as set the inline style of an element. Here is an example of how you can rotate an image by 90 degrees using JavaScript:

var img = document.getElementById('myImage');
img.style.transform = 'rotate(90deg)';
In this example, ‘myImage’ is the id of the image element you want to rotate. The transform property is used to apply 2D or 3D transformation to an element. The rotate() function rotates an element clockwise or counterclockwise according to a given degree.

Can I generate a random number with CSS?

CSS is a style-sheet language used for describing the look and formatting of a document written in HTML. It is not a programming language and does not have the capability to generate random numbers. To generate random numbers, you would need to use a programming language like JavaScript.

How can I rotate images randomly using JavaScript?

To rotate images randomly using JavaScript, you would need to generate a random number and use that as the degree of rotation. Here is an example of how you can do this:

var img = document.getElementById('myImage');
var degree = Math.floor(Math.random() * 360);
img.style.transform = 'rotate(' + degree + 'deg)';
In this example, Math.random() is used to generate a random number between 0 (inclusive) and 1 (exclusive). This number is then multiplied by 360 to get a random degree of rotation. Math.floor() is used to round down to the nearest whole number.

How can I use CSS3 to rotate an image?

CSS3 introduced the transform property, which allows you to rotate, scale, move, skew, etc., elements. To rotate an image, you can use the rotate() function. Here is an example of how you can rotate an image by 45 degrees using CSS3:

img {
transform: rotate(45deg);
}
In this example, the rotate() function rotates the image element clockwise by 45 degrees.

How can I rotate an image continuously using CSS?

To rotate an image continuously using CSS, you can use the animation property in combination with the @keyframes rule. The animation property is a shorthand property for eight of the animation properties, including animation-name, animation-duration, animation-timing-function, etc. The @keyframes rule is used to create animations. Here is an example of how you can rotate an image continuously:

img {
animation: spin 2s linear infinite;
}

@keyframes spin {
from {transform:rotate(0deg);}
to {transform:rotate(360deg);}
}
In this example, the animation property specifies that the animation called spin should complete in 2 seconds, should have a linear speed curve, and should repeat indefinitely.

How can I rotate an image on hover using CSS?

To rotate an image on hover using CSS, you can use the :hover pseudo-class in combination with the transform property. The :hover pseudo-class selects an element when the user’s pointer is over it. Here is an example of how you can rotate an image by 180 degrees when the user hovers over it:

img:hover {
transform: rotate(180deg);
}
In this example, the transform property is used to rotate the image element by 180 degrees when the user hovers over it.

How can I rotate an image back and forth using CSS?

To rotate an image back and forth using CSS, you can use the animation property in combination with the @keyframes rule. Here is an example of how you can rotate an image back and forth:

img {
animation: swing 1s infinite alternate;
}

@keyframes swing {
from {transform:rotate(-30deg);}
to {transform:rotate(30deg);}
}
In this example, the animation property specifies that the animation called swing should complete in 1 second, should repeat indefinitely, and should reverse direction each cycle.

How can I rotate an image at a constant speed using CSS?

To rotate an image at a constant speed using CSS, you can use the animation property in combination with the @keyframes rule. The animation-timing-function property can be used to specify the speed curve of the animation. Here is an example of how you can rotate an image at a constant speed:

img {
animation: spin 2s linear infinite;
}

@keyframes spin {
from {transform:rotate(0deg);}
to {transform:rotate(360deg);}
}
In this example, the animation-timing-function property is set to linear, which means the animation has a constant speed from start to end.

How can I rotate an image by a specific amount on click using JavaScript?

To rotate an image by a specific amount on click using JavaScript, you can add an event listener to the image element that listens for the click event and rotates the image when the event is fired. Here is an example of how you can rotate an image by 90 degrees when it is clicked:

var img = document.getElementById('myImage');
img.addEventListener('click', function() {
img.style.transform = 'rotate(90deg)';
});
In this example, the addEventListener() method is used to attach a click event to the image element. When the image is clicked, the function is executed, which rotates the image by 90 degrees.