Introduction

Last week, we were talking about HTML.
We said any HTML document needs to have a head tag and a body tag, and then we went over tags that are allowed to appear in the head of HTML document such as title, meta, link, and base tags.
After this we discussed some of the tags that can appear in the body of a document, h1-h6, section, figure, div, p, blockquote, ul/li, ol/li, a, img, span, br, b, u, sub, sup.
We then discuss tables which are built using the table, caption, tr, th, td tags. We looked at the colspan and rowspan attributes.
We concluded last Wednesday, discussing the WAI (Web Accessibility Initiative) and their Web Content Accessibility Guidelines (WCAG 1.0), (WCAG 2.0), (WCAG 2.1), (WCAG 3.0), and (WAI-ARIA).
We begin today by discussing accessibility and tables.

Tables and Accessibility

Tables can be a nightmare for screen readers because it is very hard for them to predict the reading order of the text.
The now obsolete summary attribute of the table tag was used for accessibility in XHTML 1.1 and below. Its value was supposed to be a screen readable summary of what the table contains.
Sometimes a distinction is made between data tables and layout tables. A data table always has headings for each row and column. A table which does not do this is assumed to be for layout purposes.
Layout tables are discouraged by WAI, where they say CSS should be used to control presentation.
If you want to make a data table accessible, it should have either a caption tag like we saw in the example a few slides back or the table should be surrounded by a figure tag and the figure should have a figcaption.
For data tables to be accessible, each row and column should have a header.
To handle fancier tables which might have nested headers or headers spanning several rows and columns, a <td> cell should use the attribute headers="" to list separated by spaces which id's of which row and column headers apply. I.e., the <th id='cat-column'>Cats</th>, ..., <th id='dog-row'>Dogs</th>, then later <td headers="cat-column dog-row">.
Another way to achieve accessibility on cells, is to use the scope="" attribute on the <th> tags with values from row, col, rowspan, colspan to say what things the cell is a header for. For example, <th scope="row"> says the header applies to the whole row.

Controlling width

In the older XHTML 1.1, you can control the width and border of tables using its width and border attributes. For example:
```
<table width="100%" border="0"  summary="..." >
```
the value can be a percentage or an absolute value in pixels. 0 here means no border.
In HTML 5, the above should be done with CSS (described later). In HTML 5, the border attribute can only take a value of 0 or 1 to indicate the presence of a border or not.

You can control the width of columns by having after the table tag a series of col tags (can also use colgroup)

<table width="100%" border="0"  summary="..." >
<col width="25%" /> <!-- can be a percentage or number of pixels -->
<col width="75%" />

Again, in HTML 5 the width attribute of a col tag should not be used. In HTML 5, the col tag still exists to indicate one wants to apply a style to a whole column.

Still More on Tables

The align and valign attributes of <tr><th><td> can be use to specify how data look within a cell. align has three possible values left, right, center (default) which control horizontal alignment. Again, these are XHTML 1.1, not HTML 5 attributes.

Ex:

<tr align="center"><td>hi<td><td>there</td></tr>
 <!-- centers whole row -->

Ex:

<td valign="top">test</td> 
<td valign="bottom">test</td>

Cellpadding, cellspacing

In XHTML 1.1 (not HTML 5), <table> also has two attributes cellpadding and cellspacing.

cellpadding
controls space between inner walls of cell and contents of the cell (in pixels).

cellspacing
controls distance between cells

Ex:

<table border="5" cellspacing="30" cellpadding="5" summary="..." >

Forms

Forms are one of the most common ways to collect data in an XHTML page and send it back to the server.

The basic format for a form is:

<form name="myform" method="get" action="http://somewhere.com" >
<!-- widgets or controls on form -->
</form>

In the case of uploading a file you also need to give the enctype attribute as "multipart/form-data"
If the method attribute is not present it is assumed to be get, if the action attribute is absent the form is sent to where it came from when it is submitted.
You can use relative urls such as "/formhandler.php", "/", ".", "..".

Possible methods

The method attribute of a form can be one of "get" or "post".
The default is get.
If the method is "get" then data collected from the form will be appended to the URL given in the action when the form is submitted:
```
http://somewhere.com/?name1=value1&name2=value2...
```
The names and values are "urlencoded" to handle special characters like space.
There used to be size limits on GET data.
GET is non-stateful though so you can send the data as a url whether or not it ever came from a form.
If the method is post. Then the HTTP POST command is used and data is sent in the body of the request after the headers.

Labels and Controls

The basic form control is input:

<input type="text" name="my variable" value="optional default value" />

Possible values for type include: checkbox, radio, text, hidden, password, reset, submit.
submit is used to submit the form.
The value attribute of input must be set if the variable is checkbox or radio. The value will be what is sent if the field is checked or selected. The checked attribute controls if it is selected by default. Only one value set for radio.
For text and password, the size and maxlength attributes control the visible size and the maximum number of input characters. (There is also a less useful minlength attribute.)
Usually, a form item is placed by some label when it is drawn
```
First Name: [             ]
```
In order to ensure this in accessibility situations you must use the label tag:
```
<label for="testid" >First Name :</label> <input type="text" 
    id="testid" name="test" value="test" />
```

Alternatively, for some form elements like search boxes you can use a title attribute for accessibility:

<input type="text" id="search" name="search" 
    title="Enter your search terms" placeholder="Enter your search terms"/>

The placeholder attribute above is an HTML 5 attribute. It causes the provided value text to be displayed in the textfield until it is focused.

In-Class Exercise

You have been commissioned to create an HTML 5, accessible, RSVP form for the CS 174 Soirée.
This form should collect the attendee's first name, last name, whether they will be bringing a significant other (checkbox), and what color jello they prefer (red, green, or yellow) (radio buttons).
Text fields should have a size and maxlength specified.
Please post your solution to the Sep 7 In-Class Exercise thread.

select tags

<textarea>

This tag can be used to specify a multi-line region for text entry:

<textarea name="life" rows="3" cols="40" >
You can enter your life story here.
</textarea>

<button>

<button type="button"><b>My Bold Button</b></button>

Button's can be of type button, submit, or reset.
submit and reset behave like <input> tags of type submit, or reset, but maybe are semantically more clear. They also allow you to put tags around the button's text like the b tags we used above.
Like input tags can have name adnd value attributes.
Type button can be used when you want a button, but don't want it associated with a form.

Stylesheets

We now return to talking about XHTML, in particular, how to control the presentation of XHTML documents with stylesheets.
Stylesheets are used to specify the look of the page and its elements.
For instance, one can globally control things like margins, indentation, etc.
They can be used to support the idea of separating structure of content from how it is presented.
Cascading Style Sheets (CSS) are the standard way to do this for XHTML documents.
CSS comes in four specs: CSS1, CSS2 (2.1 became a recommendation), CSS3, CSS4 each adding more features to the last.
Most modern browsers support CSS1, most CSS2.1, and some of CSS3 and CSS 4.
Beginning with CSS 3, new features are split into modules of different "levels". A module is level 3, if it depends on CSS 2.1, and level 4 (i.e., part of CSS4) if it depends on a level 3 module. For example, there is both a CSS Level 3 Selector Module and a CSS Level 4 Selector Module.
CanIUse.com is a good website for seeing what browsers support which more sophisticated feature.
The basic concept in a stylesheet is that of the value of a property that a tag has.
Cascading refers to how settings of this value in high level stylesheets can be overrriden in lower level style sheets.

More HTML Body Tags - Tables - Accessibility

Outline