Doing so may actually interfere with how assistive technology parses the button input. This means that, for example, a screen reader will read out the label when the user is focused on the form input, making it easier for an assistive technology user to understand what data should be entered.
That increased hit area for focusing the input provides an advantage to anyone trying to activate it — including those using a touch-screen device. Content categories Flow content , phrasing content , interactive content , form-associated element , palpable content. Permitted content Phrasing content , but no descendant label elements. User agents should be able to find anchors created by empty A elements, but some fail to do so. For example, some user agents may not find the "empty-anchor" in the following HTML fragment:.
An anchor name is the value of either the name or id attribute when used in the context of anchors. Anchor names must observe the following rules:.
Thus, the following example is correct with respect to string matching and must be considered a match by user agents:. Although the following excerpt is legal HTML, the behavior of the user agent is not defined; some user agents may incorrectly consider this a match and others may not. Links and anchors defined by the A element must not be nested; an A element must not contain any other A elements.
The id attribute may be used to create an anchor at the start tag of any element including the A element. This example illustrates the use of the id attribute to position an anchor in an H2 element. The anchor is linked to via the A element. The following example names a destination anchor with the id attribute:.
The id and name attributes share the same name space. This means that they cannot both define an anchor with the same name in the same document. When both attributes are used on a single element, their values must be identical. The following example illustrates that id and name must be the same when both appear in an element's start tag:.
The id attribute, on the other hand, may not contain character references. Use id or name? Authors should consider the following issues when deciding whether to use id or name for an anchor name:. A reference to an unavailable or unidentifiable resource is an error. Although user agents may vary in how they handle such an error, we recommend the following behavior:. This element defines a link. Unlike A , it may only appear in the HEAD section of a document, although it may appear any number of times.
Although LINK has no content, it conveys relationship information that may be rendered by user agents in a variety of ways e. The current document is "Chapter2. The rel attribute specifies the relationship of the linked document with the current document. The values "Index", "Next", and "Prev" are explained in the section on link types. The rel and rev attributes play complementary roles -- the rel attribute specifies a forward link and the rev attribute specifies a reverse link.
When the LINK element links an external style sheet to a document, the type attribute specifies the style sheet language and the media attribute specifies the intended rendering medium or media. User agents may save time by retrieving from the network only those style sheets that apply to the current device. Media types are further discussed in the section on style sheets. It is also used by JavaScript to access and manipulate the element with the specific id.
The syntax for id is: write a hash character , followed by an id name. Note: The id name must contain at least one character, cannot start with a number, and must not contain whitespaces spaces, tabs, etc. The id attribute can also be used by JavaScript to perform some tasks for that specific element. JavaScript can access an element with a specific id with the getElementById method:. This was fine for most situations, but it became annoying when you wanted, for example, to turn an entire advertising banner section containing images and paragraphs into a link.
For the code to remain valid, you would have to wrap each individual bit of text and each image in its own separate link — all going to the same place — which is not only horribly repetitious, but confuses assistive technology and its users.
Putting an inline element around a section of block level content also makes styling behave weirdly, unless you remember to set it to display like a block level element using CSS. Fortunately, HTML5 removes this restriction, allowing you to put a single link around any amount of content you want. To get it to behave properly, you still have to set the link to behave like a block level element, but this is easy, and far more flexible than it used to be. I have also added a background-color change on hover to make this more visible.
We covered a lot in this article, but perhaps the most important takeaway is to remember not only what links do, but what they should do. Notice: The WebPlatform project, supported by various stewards between and , has been discontinued.
This site is now available on github. DOCS guides html links. What are links? The anchor tag has several attributes you can add: href — the resource the link points to either an external file or an anchor ID. This attribute can contain different values: A URL relative to the current folder, e.
A fragment identifier or id preceded by a hash sign, e. This points to a target inside the current document rather than an external URL. A mixture of URLs and fragment identifiers. To recap: Anchor links can have a fragment identifier as the value of the href attribute. This fragment identifier must start with a hash sign. When activated, this link will jump to any HTML element with an id of this value.
All IDs on a page must be unique. IDs follow certain naming conventions. Most important is that they must start with an alphanumeric character and must not contain spaces. Leaving the current site and linking to another server external links.
0コメント