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Accessibility on the web has been an issue for over a decade, and it remains a crucial--but often overlooked--element of web design. Instructor Zoe Gillenwater explains the concept of accessibility as it applies to the web, and describes how it affects the audience. She also covers how to set up accessibility testing, and how to apply accessibility principles to new and existing sites using standards-compliant markup and CSS. Exercise files accompany the tutorials.
>> So far in this chapter we have talked a lot about screen readers and improving accessibility for there users. This is not because any disability is more important than another but primarily because screen reading is such a different experience from other types of browsing that it can require more accommodation and changes to our pages. In this and the next movie however we'll be focusing on issues that have no bearing on screen reader access, how to make the appearance of our text easier to read. There are many web users who are not blind and do not use screen readers but have other visual impairments or simply poor vision and may find text hard to read.
In this movie we will focus on the sizing and spacing of text for readability. If you are following along in the exercise files we're working on the file visitors.html in the 04 06 folder of the chapter four exercise files. We're going to set a base font size for this page. The size units that we choose for our text should always be relative units. Those are units that have no set dimensions but change in size based on each platform, browser and user setting.
The two main relative units for text are percentages and em's. We've talked about the em unit earlier as being relative to the size of the text characters. One em equals whatever the current font size is, so if the user has a font size set to 16 pixels and you set the font on your webpage to on em, he or she will see 16 pixel text. Percentages are relative to the font size of the parent element. The parent element is simply the HTML tag that is wrapping around the current tag that you are in.
If there is no parent element, for instance you are on the body tag or if the parent element has no font size set the percentage is simply relative to the users browsers default size. Once again setting 100 percent would simply equal their default setting. That makes em's and percentages pretty interchangeable. You can use whichever one makes more since to you. Leavening the text set as 100 percent or one em is the most accessible option because if the user has configured their size to their preferences, you are respecting their preference and not making the text smaller than they can or prefer to read.
In reality though very few users ever change their browser or system font size simply because they don't know they can and most clients aren't going to be happy with how large text is if you leave it at the default. Not to mention you as a web designer might not be too happy about it, so the compromise is to set text to a lower size. But to keep accessibility in mind don't make it too small and make sure that you keep it in relative units. If you use an absolute unit such as pixels to size the text, internet explorer users won't be able to change the text size, all other browsers allow pixel text sizes to be scaled but it is still good to pick a percentage of em value instead of an arbitrary pixel value that could end up being really far off from what a user has set for him or herself.
With that in mind let's choose a smaller font size for our main body text. We want to pick a measurement that will be roughly the same between different browsers. Each one is going to have to round the value that we choose. Open up your system calculator, on windows go to the start menu, click on all programs, then click on accessories and choose calculator. The default font size on most systems and therefore the size that most users will have set is 16 pixels.
Let's see what font size we would end up with if we chose a percentage value of 90 percent. Type in 16 and multiply it by .9, we get 14.4, there's no way for the browser to make texts that contain fractions of pixels so it's going to have to round this number. Every browser will round in a different way so we'd like to get the value as close as possible to a whole number. Let's try 88 percent, hit clear then type 16 times .88.
That gives us 14.08. This is the closest we are going to get to a whole pixel value so this is probably a good value to pick. Close the calculator and go back to Dreamweaver, in the CSS styles panel click on the body rule at the top of the all rules pane. In the properties listed below you'll see that the font property is currently being set. The first values listed for font is 100 percent, this is the font size we are now going to change to 88 percent, click on the number and the text field becomes editable, you may need to scroll back over to the front of the field to see 100 percent.
Highlight over and type 88, make sure you leave the percentage mark. Hit enter or return to accept the value, you'll see that all the text has now changed size because we set the size of the heading text in percentages as well, it also scales down proportionally. Another change we can make to the text that affects it readability is the amount of white space between each of the lines of text. We've already modified the margins on the headings to improve the spacing between the chunks of text, but now let's increase the space in between all lines of text on the page using the line height property.
We'll set this on the body rule as well. With the body rule still selected in the CSS styles panel click on the add property link in the properties area of the panel, type in line but then click the arrow on the menu to bring up a list of CSS properties. Dreamweaver already highlighted line height for us. Click on that property name and your cursor is now in a new box for you to enter the value. Type in 1.6 this means that each line of text will be 1.6 times the height of a single line of text away from each other.
The next box is asking us to set a unit. We actually don't want to set a unit for the line height property, by leaving off a unit we ensure that it will always be 1.6 times whatever font is set wherever on the page. So leave it set to multiple. You can see in the design view that there is now extra space in between the lines of text. This white space makes the text easier to read. So we now addressed the accessibility aspects of sizing and spacing text. Lets next look at how color of text affects it readability.
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