Hacker's lounge: Alt Attribute & SEO Optimization

SEO Optimization images is becoming more and more essential in SEO (Search Engine Optimization) for websites. The ALT attribute is a critical step that is often overlooked. This can be a lost chance of better rankings.

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

Images:. Make use of the alt attribute to provide descriptive text. Additionally, we recommend using a human-readable caption and descriptive text round the image.

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

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

On the other hand, high keyword density can, on some search engines like google, trigger spam filters, which may create a penalty for the site's ranking. Even without this type of penalty, your site's rankings won't benefit from this plan.
This method also puts persons who use screen readers in a greater disadvantage. Screen readers are software-based tools that really read aloud the items in what is shown on the screen. In browsing the net, the alt features of images are read aloud too.

Imagine hearing a paragraph of text which is then repetitions of numerous keywords. The page will be not even close to accessible, and, to put it mildly, will be found quite annoying.
What exactly is an Alt attribute?

An ALT attribute should not be used as a description or perhaps a label to have an image, though many people utilize it for the reason that fashion. Though it may appear natural to assume that alternate text is a label or a description, it's not!

The words used within an image's alt attribute should be its text equivalent and convey the same information or serve the same purpose the image would.

The goal would be to provide the same functional information that a visual user would see. The alt attribute text should be the "stand in" in the event that the look itself is not available. Ask yourself this: If you were to replace the look using the text, would most users get the same basic information, and wouldn't it create the same response?
A few examples:

Some SEO Optimization Tips

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

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

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

If it is meant to convey using a function, then the function is what ought to 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 within the page, make use of an empty alt (i.e. alt="") or a CSS background image to ensure that reading browsers don't bother users by uttering such things as "spacer image".

Keep in mind that it is the function from the image we are trying to convey. For example; any button images should not include the word "button" within the alt text. They ought to emphasize the action performed by the button.

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

Attempt to flow alt text with the remainder from the text because that is how it will be read with adaptive technologies like screen readers. Someone listening to your page should hardly be aware that a graphic image is there.
Please remember that using an alt attribute for each image is needed to meet the minimum WAI requirements, that are used since the benchmark for accessibility laws in UK and also 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 apart from to make a site visually appealing/attractive and (oftentimes) satisfy the marketing departments. There isn't any content value (though there might be value to some sighted user).

Never alt-ify eye-candy unless there is something there which will boost the usability from the site for somebody using a non-visual user agent. Make use of 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 the stage so to speak. These graphics are not direct content and may not be considered essential, but they're essential in they help frame what is going on.

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

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

Usually this will depend on context. The same image in a different context may need drastically different alt text. Obviously, content ought to always be fully available. How you use this case is 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 so as.
The reason many authors can't figure out why their alt text isn't working is they don't know why the pictures exist. You have to figured out exactly what function an image serves. Think about what it is concerning the image that's important to the page's intended audience.

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

Aside from the alt attribute you've got 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 may add flavor. The title attribute is optionally rendered by the user agent. Remember they are invisible and never shown like a "tooltip" when focus is received via the keyboard. (So much for device independence). So use the title attribute only for advisory information.
Second, the longdesc attribute points to the Link to a full description of an image. When the information contained in an image is essential towards the meaning of the page (i.e. some important content will be lost if the image was removed), a longer description compared to "alt" attribute can reasonably display ought to be used. It may provide for rich, expressive documentation of the 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 an image...The aim is by using any period of description essential 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 holds true even for that totally blind."

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

Oftentimes, you're best just going with your gut instinct -- if it's not necessary to include 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 whole 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 your image and its context about the page.

Exactly the same image may need alt text (or title or longdesc) in a single spot, although not in another. If an image provides absolutely no content or functional information alt="" or background CSS images might be appropriate to make use of. But if the image provides content or adds functional information an alt will be required and perhaps even a long description will be in order. Oftentimes this type of thing is really a judgement call.