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 sometimes forgotten. This is often a lost chance of better rankings.
In Google's webmaster guidelines, they advise using alternative text for that images in your site:
Images:. Make use of the alt attribute to supply descriptive text. Additionally, we recommend using a human-readable caption and descriptive text around the image.
Why would they ask us to achieve that? The answer is simple, really; search engines like google have a similar problem as blind users. They cannot 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 certain keyword density, which is not as relevant for rankings now as it once was.
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 such a penalty, your site's rankings will not benefit from this tactic.
This method also puts persons who use screen readers at a greater disadvantage. Screen readers are software-based tools that actually read aloud the items in what is displayed on the screen. In browsing the web, the alt features of images are read aloud too.
Imagine listening to 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, would be found quite annoying.
What exactly is an Alt attribute?
An ALT attribute shouldn't be used as a description or a label to have an image, though many people use it for the reason that fashion. Though it may appear natural to assume that alternate text is a label or a description, it is not!
The words used within an image's alt attribute should be its text equivalent and convey exactly the same information or serve the same purpose the image would.
The thing is to supply 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 itself is unavailable. Think about this question: If you were to replace the look using the text, would most users get the same basic information, and wouldn't it generate the same response?
Some examples:
If a search button is a magnifying glass or binoculars its alt text ought to be 'search' or 'find' not 'magnifying glass' or 'binoculars'.
If the image is supposed to convey the literal contents of the look, a description is suitable.
If it is designed to convey data, then that information is what is appropriate.
If it's designed 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 in the page, use an empty alt (i.e. alt="") or a CSS background image to ensure that reading browsers don't bother users by uttering things like "spacer image".
Remember that it is the function from the image we're trying to convey. For example; any button images should not include the word "button" in the alt text. They should emphasize the action performed through the button.
Alt text should be based on context. The same image in a different context may require drastically different alt text.
Attempt to flow alt text with the remainder from the text because that's how it will 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 using 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 the rest of Europe. Also, they are 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 make a site visually appealing/attractive and (in many cases) fulfill the marketing departments. There is no 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 of 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 actually set the mood or set the stage as it were. These graphics are not direct content and may 't be considered essential, but they are essential in that they help frame what is going on.
Attempt to alt-ify the 2nd group as makes sense and is relevant. There might be times when doing so may be annoying or detrimental with other users. Then try to avoid it.
For example; Alt text that's 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 understand this content in there for those users.
Most times it depends on context. Exactly the same image in a different context may require 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 when the look is the actual content. Always alt-ify content and functional images. Title and long description attributes can also be so as.
The main reason many authors can't understand why their alt text isn't working is they don't know why the pictures exist. You need to determined exactly what function a picture 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 enhances the theme/ mood/ atmosphere or it is critical 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 over the telephone to someone. An amount you say when encountering a particular image to make the page understandable to the listener?
Besides the alt attribute you have a couple more tools at your disposal for images.
First, in degree of descriptiveness title is within between alt and longdesc. It adds useful information and can add flavor. The title attribute is optionally rendered through the user agent. Remember they are invisible and not shown like a "tooltip" when focus is received through the keyboard. (A lot for device independence). So make use of the title attribute just for advisory information.
Second, the longdesc attribute points towards the Link to a full description of the image. When the information found in an image is important to the meaning of the page (i.e. some important content would be lost if the image was removed), a longer description than the "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 an 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 would not be remiss to hope that a long description conjures a picture - the look - in the mind's eye, an analogy that is 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.
Oftentimes, 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 include that longdesc.
However, if it's necessary for the entire page to work, then you've to add the alt text (or title or longdesc).
What's necessary and what's not depends a great deal about the function of your image and it is context on the page.
The same image may require alt text (or title or longdesc) in a single 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. But if the image provides content or adds functional information an alt would be required and perhaps even a long description will be so as. In many cases this kind of thing is a judgement call.
Listed here are key steps in optimizing images:
Choose a logical file name that reinforces the keywords. You should use hyphens within the file name to isolate the keyword, but avoid to exceeding two hyphens. Avoid using underscores like a word separator, such as "brilliant-diamonds.jpg";
Label the file extension. For instance, if the image internet search engine sees a ".jpg" (JPEG) file extension, it's going to assume that the file is a photo, and when it sees a ".gif" (GIF) file extension, it's going to assume that it is a graphic;
Make sure that the text nearby the image that is highly relevant to that image.
Again, don't lose an excellent chance to help your website together with your images in search engines. Begin using these steps to position better on all of the engines and drive increased traffic to 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.
andyrussell Says:
May 18, 2011 at 8:43 am
Ok, so I’m probably not giving DTR as much significance as it deserves.
My point is that I don’t really care about DTR. I don’t think I know anyone who has a particular interest in DTR. If this paper had been published by anyone else I wouldn’t have looked at it. It’s not very interesting. It’s just another paper on climate observations that fits in with the “consensus view of climate change” or however you want to put it. That’s useful, but not to me or most people.
If, however, the paper had shown what Watts has been saying it would show for quite a while now (i.e. that the postitive temperature trend in the surface station record in the US was an artefact of poor station siting) then that would have been very interesting. To me and to many other people.
But it didn’t.
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.