About Me 0050: Alt Attribute & Search engine optimization

SEO Optimization images is becoming increasingly more essential in SEO (Search Engine Optimization) for websites. The ALT attribute is a critical step that is sometimes forgotten. This can be a lost opportunity for better rankings.

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

Images:. Use the alt attribute to supply descriptive text. Additionally, we recommend using a human-readable caption and descriptive text round the image.

Why would they ask us to achieve that? The answer is easy, really; search engines have the same problem as blind users. They cannot begin to see the images.

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

On the contrary, high keyword density can, on some search engines, trigger spam filters, which may result in a penalty for the site's ranking. Even without such a penalty, your site's rankings will not take advantage of this plan.
This method also puts persons who use screen readers in a greater disadvantage. Screen readers are software-based tools that actually read aloud the contents of what's shown on the screen. In browsing the web, the alt attributes of images are read aloud as well.

Imagine hearing a paragraph of text which is then repetitions of numerous keywords. The page would 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 to have an image, though lots of people utilize it for the reason that fashion. Though it might seem natural to assume that alternate text is a label or a description, it's not!

What used inside an image's alt attribute should be its text equivalent and convey the same information or serve exactly the same purpose that the image would.

The thing would be to provide the same functional information that a visual user would see. The alt attribute text should be the "stand in" when the image is not available. Think about this question: If you were to replace the image with the text, would most users get the same basic information, and would it generate the same response?
A few examples:

Some SEO Optimization Tips

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

If an image is meant to convey the literal items in the image, then a description is suitable.

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

If it is 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 as well as for valid XHTML.

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

Keep in mind that it is the function of the image we're attempting to convey. For instance; any button images should not range from the word "button" within the alt text. They should emphasize the action performed by the button.

Alt text should be determined by context. The same image inside a different context may require drastically different alt text.

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

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) satisfy 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 enhance the usability from the site for someone utilizing a non-visual user agent. Use a null alt attribute or background images in CSS for eye-candy.

II. Mood-Setting

This is the middle layer of graphics which might actually set the atmosphere or set happens as it were. These graphics aren't direct content and could not be considered essential, but they are important in that they help frame what is going on.

Try to alt-ify the second group as is sensible and it is relevant. There might be instances when doing this might be annoying or detrimental to other users. Then try to avoid it.

For instance; Alt text that is just like adjacent text is unnecessary, as well as an irritant to screen reader users. I recommend alt="" or background CSS images in such instances. But sometimes, it's vital that you understand this content inside for all users.

Most times it depends on context. The same image inside a different context may require drastically different alt text. Obviously, content should always be fully available. How you go in this case is a judgment call.

III. Content and Function

This is when the look may be the actual content. Always alt-ify content and functional images. Title and long description attributes can also be in order.
The reason many authors can't understand why their alt text isn't working is they don't know why the images exist. You have to figured out precisely what function an image serves. Consider what it's about the image that's important to the page's intended audience.

Every graphic has a reason for standing on that page: because it either improves the theme/ mood/ atmosphere or it is critical to what are the page is attempting to explain. Understanding what the image is for makes alt text simpler to write. And practice writing them definitely helps.
A method to check the usefulness of alternative text is to imagine reading the page over the telephone to someone. An amount you say when encountering a specific image to make the page understandable towards 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 in between alt and longdesc. It adds useful information and can add flavor. The title attribute is optionally rendered by the user agent. Remember they are invisible and not shown like a "tooltip" when focus is received via the keyboard. (A lot for device independence). So use the title attribute only for advisory information.
Second, the longdesc attribute points to the URL of a complete description of the image. If the information contained in an image is essential to the concept of the page (i.e. some important content will be lost if the image was removed), a longer description than the "alt" attribute can reasonably display ought to be used. It can provide for rich, expressive documentation of a visual image.

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

It would not be remiss to hope that a long description conjures an image - the image - in the mind's eye, an analogy that holds true even for the totally blind."

Although the alt attribute is mandatory for web accessibility and for valid (X)HTML, not every images need alternative text, long descriptions, or titles.

In many cases, you're best just choosing your gut instinct -- if it's not essential to incorporate it, and if you don't possess a strong urge to get it done, don't include that longdesc.

However, if it's necessary for the whole page to work, then you have to add the alt text (or title or longdesc).

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

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