SEO Optimization images has become more and more essential in SEO (Search Engine Optimization) for websites. The ALT attribute is really a critical step that is often overlooked. This can be a lost opportunity for better rankings.
In Google's webmaster guidelines, they advise using alternative text for the images on your site:
Images:. Use the alt attribute to provide descriptive text. In addition, we recommend using 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 using this attribute, attempting 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 contrary, high keyword density can, on some search engines, trigger spam filters, which may result in a penalty for your site's ranking. Even without this type of penalty, your site's rankings will not benefit from 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 too.
Imagine listening to a paragraph of text which is then repetitions of many keywords. The page would be far from accessible, and, to put it bluntly, will be found quite annoying.
What is an Alt attribute?
An ALT attribute shouldn't be used like a description or perhaps a label for an image, though lots of people utilize it in that fashion. Though it may appear natural to assume that alternate text is a label or perhaps a description, it is 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 that the image would.
The goal is to supply the same functional information that the visual user would see. The alt attribute text should function as a "stand in" in the event that the look is unavailable. Think about this: Should you replace the look with the text, would most users get the same basic information, and wouldn't it create the same response?
Some examples:
If a search button is really a magnifying glass or binoculars its alt text should be 'search' or 'find' not 'magnifying glass' or 'binoculars'.
If the image is supposed to convey the literal items in the look, then a description is suitable.
If it's designed to convey data, then that data is what is 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 as well as for valid XHTML.
For images that play only a decorative role within the page, use an empty alt (i.e. alt="") or perhaps a CSS background image so that reading browsers don't bother users by uttering such things as "spacer image".
Remember that it's the function of the image we are attempting to convey. For example; any button images shouldn't include the word "button" in the alt text. They ought to 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.
Try to flow alt text with the rest of the text because that is how it will be read with adaptive technologies like screen readers. Someone listening to your page should hardly remember that a graphic image can there be.
Please remember that using an alt attribute for each image is needed to satisfy the minimum WAI requirements, which are used as the benchmark for accessibility laws in UK and also the remainder of Europe. They are also necessary to meet "Section 508" accessibility requirements in america.
It is important 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 create a site visually appealing/attractive and (oftentimes) fulfill the marketing departments. There is no content value (though there might be value to a sighted user).
Never alt-ify eye-candy unless there's something there which will boost the usability from the site for someone 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 might serve to set the mood or set the stage as it were. These graphics are not direct content and could 't be considered essential, but they're essential in that they help frame what's going on.
Try to alt-ify the 2nd group as makes sense and it is relevant. There may be times when doing this may be annoying or detrimental with other users. Then avoid it.
For instance; Alt text that is just like adjacent text is unnecessary, and 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 ought to always be fully available. The way you use this example is really a judgment call.
III. Content and Function
This is where 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 main reason many authors can't understand why their alt text isn't working is they don't know why the images exist. You need to determined precisely what function an image serves. Consider what it is about the image that's vital that you the page's intended audience.
Every graphic has a reason behind standing on that page: since it either enhances the theme/ mood/ atmosphere or it is critical to what are the page is trying to explain. Understanding what the look is perfect for makes alt text easier to write. And practice writing them definitely helps.
A way to check the usefulness of alternative text is to imagine reading the page on the phone to someone. What would you say when encountering a particular image to make the page understandable towards the listener?
Besides the alt attribute you've got a couple more tools available for images.
First, in degree 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're invisible and never shown like a "tooltip" when focus is received via the keyboard. (A lot for device independence). So use the title attribute just for advisory information.
Second, the longdesc attribute points to the URL of a full description of an image. If the information contained in an image is important 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 should 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 to use any period of description necessary to impart the details from the graphic.
It would not be remiss to hope that the long description conjures a picture - the image - in 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 all images need alternative text, long descriptions, or titles.
In many cases, you're best just choosing your gut instinct -- if it's not necessary 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 essential for the whole page to operate, 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 your image and it is context about the page.
The same image may need alt text (or title or longdesc) in one spot, but not in another. If the image provides absolutely no content or functional information alt="" or background CSS images might be appropriate to make use of. However, if the image provides content or adds functional information an alt will be required and maybe a long description will be in order. In many cases this type of thing is a judgement call.
Listed here are key stages in optimizing images:
Choose a logical file name that reinforces the keywords. You should use hyphens in the file name to isolate the keyword, but avoid to exceeding two hyphens. Avoid using underscores as a word separator, like for example "brilliant-diamonds.jpg";
Label the file extension. For instance, when the image search engine sees a ".jpg" (JPEG) file extension, it's likely to assume that the file is really a photo, and when it sees a ".gif" (GIF) file extension, it's going to assume that it is graphic;
Ensure that the written text nearby the image that's highly relevant to that image.
Again, do not lose an excellent chance to help your site together with your images searching engines. Begin using these steps to rank better on all of the engines and drive increased traffic for your site TODAY.
Peter Risdon Says:
May 16, 2011 at 2:40 pm | Reply
The paragraph you quoted from ends with this sentence:
“According to the best-sited stations, the diurnal temperature range in the lower 48 states has no century-scale trend.”
That was a surprise given the tenor of this post: “… maybe this is the end to questions as to whether surface temperature increases actually exist.”
Did you mean that we can now say the answer to that is that surface temperature increases do not exist? Or that, pace Keenan in the WSJ, the data do not contain statistically significant trends?
andyrussell Says:
May 16, 2011 at 2:58 pm | Reply
I don’t think diurnal temperature range is very important. Do you?
What’s more, the “century-scale” bit covers some interesting detail. Before Fall et al., it seems that the only work on diurnal temperature range showed a negative trend from the mid-century to 1980s-ish. What Fall et al. found was that this has increased again since the 1980s. So there’s no “century-scale trend”.
But that tells you very little about mean surface temperature trends.
Mark Says:
May 17, 2011 at 10:45 pm
I have heard it claimed that the reduction in diurnal temperature range over the past few decades provides evidence that GHG increases are responsible for the warming. In that sense, some people think diurnal temperature range is important.
Incidentally, I don’t think Fall et al. were the first to find that DTR has increased since the 1980s. I read a paper that said much the same thing a few years ago.
Sorry for the lack of references to back up these statements. I’m a little too busy at the moment to chase them up.
Ben Says:
May 16, 2011 at 4:49 pm | Reply
So Peter… If the diurnal high and the diurnal low both rise by 1°C, you think this means there has been no warming? After-all, the diurnal range hasn’t changed! Others might draw a different conclusion.
Peter Risdon Says:
May 17, 2011 at 8:26 am | Reply
I understand diurnal range has significance, and the relationship between day and night time temperature ranges is important, especially with regard to the period 1950 to 1980 when the effect of man-made global warming, it has been argued, was masked by a cooling but revealed by the changes in the relationship between these ranges.
I further understand that this argument is based on the idea that human pollution caused this daytime cooling, that it affected the range of day time temperatures as well as the difference between night time temperatures which continued to show warming, and daytime ones that didn’t. This makes day time temperature range significant: if this is right it would be expected to show a variation that correlates with human activity.
But this isn’t my field; I’m just reading what I can in an attempt to understand as much as possible about an important issue and, for me at least, that means reading Watts and reading this blog. Just searching out stuff you’re already disposed to accept isn’t good enough. My comment was prompted by what struck me as a somewhat partial quotation and exasperation: I’m with Feynman when he said you should point out the problems with a theory, not just the things that support it.
[It's not really a "partial quotation" is it? That sentence you are interested in is stuck on the end of the abstract as a new paragraph and isn't really related to the 2 sentences I quote and which are related to the subject of this post. I'm not really interested in DTR and I doubt Watts was either. - AR]
At least Watts invites people with different views to post on his blog and has been at the forefront of attempts to cross the ideological divide, not least with Judith Curry.
Ben, of course you’re right. Andy, a century is an arbitrary scale, of course.
I’d still be interested in your take on statistical significance.
JMurphy Says:
May 17, 2011 at 12:05 pm | Reply
In what way has Watts atempted to cross “the ideological divide” ?
Ben Says:
May 17, 2011 at 3:16 pm | Reply
Peter, I encourage a critical (i.e. thoughtful) reading of Anthony’s blog but my god do you really think he’s “at the forefront of attempts to cross the ideological divide”? Anthony has done more to harden denialist thought than anyone, with the possible exception Marc Morano.
The “different views” he solicits are unthreatening fig-leaves.
andyrussell Says:
May 17, 2011 at 3:24 pm | Reply
I’ve got no problem with most of what Keenan says, although he’s not the first/only person to be saying these things. There’s a JoC paper from 2010 and it was one of the useful points to come out of the UEA email enquiries (i.e. working more with stats people). Not sure where the funding was supposed to come from for these new people though!
I suppose the bigger problem comes down to climate science covering so much stuff – you can’t just look at problems from a stats/dynamics/modelling/chemistry/radiation/whatever perspective for too long before a) not getting very far or b) needing to doing something you’ve not done before.