Data Processing: Alt Attribute & SEO Optimization

SEO Optimization images is becoming more and more important in SEO (Seo optimization) for websites. The ALT attribute is a critical step that is often overlooked. This can be a lost opportunity for better rankings.

In Google's webmaster guidelines, they advise the use of alternative text for the images in your web site:

Images:. Make use of the alt attribute to provide descriptive text. In addition, we recommend utilizing a human-readable caption and descriptive text around the image.

Why would they ask us to do that? The answer is simple, really; search engines have the same problem as blind users. They can't begin to see the images.

Many webmasters and inexperienced or unethical SEOs abuse the use of this attribute, attempting to stuff it with keywords, hoping to achieve a particular keyword density, which is not as relevant for rankings now since it was previously.

On the contrary, high keyword density can, on some search engines like google, trigger spam filters, which might create a penalty for your site's ranking. Even without this type of penalty, your site's rankings will not take advantage of this tactic.
This method also puts persons who use screen readers in a greater disadvantage. Screen readers are software-based tools that really read aloud the contents of what is displayed on the screen. In browsing the net, the alt attributes of images are read aloud as well.

Imagine hearing a paragraph of text that is then repetitions of many keywords. The page will be far from accessible, and, to put it bluntly, would be found quite annoying.
What exactly is an Alt attribute?

An ALT attribute should not be used like a description or a label for an image, though lots of people utilize it in that fashion. Although it might seem natural to assume that alternate text is a label or perhaps a description, it is not!

The words used inside an image's alt attribute ought to be its text equivalent and convey the same information or serve exactly the same purpose the image would.

The goal is to provide the same functional information that the visual user would see. The alt attribute text should be the "stand in" in the event that the look is unavailable. Think about this: If you were to replace the look with the text, would most users receive the same basic information, and wouldn't it generate the same response?
Some examples:

Some SEO Optimization Tips

If your search button is a magnifying glass or binoculars its alt text should be 'search' or 'find' not 'magnifying glass' or 'binoculars'.

If an image is supposed to convey the literal contents of the image, a description is appropriate.

If it's meant to convey data, then that information is what's appropriate.

If it's meant to convey the use of a function, then the function itself is what should be used.

Some Alt Attribute Guidelines:

Always add alt attributes to images. Alt is mandatory for accessibility and for valid XHTML.

For images that play only a decorative role in the page, make use of an empty alt (i.e. alt="") or a CSS background image to ensure that reading browsers do not bother users by uttering such things as "spacer image".

Keep in mind that it is the function from the image we're trying to convey. For example; any button images shouldn't include the word "button" in the alt text. They ought to emphasize the action performed through the button.

Alt text ought to be based on context. Exactly the same image in a different context may need drastically different alt text.

Attempt to flow alt text with the rest from the text because that is how it is going to be read with adaptive technologies like screen readers. Someone hearing your page should hardly remember that a graphic image is there.
Please keep in mind that utilizing an alt attribute for every image is required to meet the minimum WAI requirements, which are used as the benchmark for accessibility laws in UK and the rest of Europe. They are also required to meet "Section 508" accessibility requirements in the US.

It is useful to categorize non-text content into three levels:

Eye-Candy
Mood-Setting
Content and Function

I. Eye-Candy

Eye-Candy are stuff that serve no purpose other than to make a site visually appealing/attractive and (oftentimes) fulfill the marketing departments. There isn't any content value (though there may be value to some sighted user).

Never alt-ify eye-candy unless there is something there that will boost the usability from the site for somebody utilizing a non-visual user agent. Use a null alt attribute or background images in CSS for eye-candy.

II. Mood-Setting

This is actually the middle layer of graphics which may serve to set the mood or set happens as it were. These graphics aren't direct content and may not be considered essential, but they're important in they help frame what's going on.

Attempt to alt-ify the 2nd group as makes sense and is relevant. There might be times when doing this might be annoying or detrimental with other users. Then avoid it.

For example; Alt text that is identical to adjacent text is unnecessary, and an irritant to screen reader users. I suggest alt="" or background CSS images in such cases. But sometimes, it's vital that you get this content in there for those users.

Most times it depends on context. Exactly the same image inside a different context may need drastically different alt text. Obviously, content should always be fully available. The way you go in this example is really a judgment call.

III. Content and Function

This is where the image may be the actual content. Always alt-ify content and functional images. Title and long description attributes can also be in order.
The main reason many authors can't figure out why their alt text isn't working is that they don't know why the pictures are there. You have to figured out exactly what function an image serves. Think about what it's about the image that's important to the page's intended audience.

Every graphic has a reason for being on that page: because it either improves the theme/ mood/ atmosphere or it is advisable to what the page is trying to describe. Understanding what the look is perfect for makes alt text simpler to write. And exercise writing them definitely helps.
A method to look into the usefulness of alternative text is to imagine reading the page over the telephone to someone. What would you say when encountering a particular image to make the page understandable to the listener?

Aside from the alt attribute you have a couple more tools at your disposal for images.
First, in level of descriptiveness title is within between alt and longdesc. It adds useful information and may add flavor. The title attribute is optionally rendered through the user agent. Remember they are invisible and not shown as a "tooltip" when focus is received through the keyboard. (So much for device independence). So make use of the title attribute just for advisory information.
Second, the longdesc attribute points to the Link to a full description of the image. When the information contained in an image is essential to the meaning of the page (i.e. some important content will be lost if the image was removed), an extended description compared to "alt" attribute can reasonably display ought to be used. It may offer rich, expressive documentation of a visual image.

It should be used when alt and title are insufficient to embody the visual qualities of the image. As Clark [1] states, "A longdesc is really a long description of the image...The aim is by using any length of description necessary to impart the details of the graphic.

It wouldn't be remiss to hope that the long description conjures an image - the look - within the mind's eye, an analogy that is true even for that totally blind."

Even though alt attribute is mandatory for web accessibility as well as for valid (X)HTML, not every images need alternative text, long descriptions, or titles.

In many cases, you're better off just going with your gut instinct -- if it's not necessary to incorporate it, and when you don't have a strong urge to get it done, don't add that longdesc.

However, if it's essential for the entire page to work, then you've to include the alt text (or title or longdesc).

What's necessary and what's not depends a lot about the function of the image and its context about the page.

The same image may require alt text (or title or longdesc) in one spot, but not in another. If an image provides absolutely no content or functional information alt="" or background CSS images may be appropriate to use. But if the image provides content or adds functional information an alt will be required and perhaps a long description would be so as. In many cases this type of thing is a judgement call.