things NN won't do

when NN fails to respond intuitively

page 7 of 8

page 1
• margins and headers
• margins and headers with width
page 2
• setting div margins in a table cell
• setting div width in a table cell
• adding a border
page 3
• setting color of text in tables
• name anchor references
page 4
• closing table tag
• span tag
• negative margins
page 5
• broken images and alt text
• the title attribute
page 6
• the height attribute
page 7
• the pseudo classes
page 8
• iframes

the pseudo-classes

One major thing that NN4.7 will not do is respond to all of the pseudo-classes. The psuedo-classes are an example of a style that degrades gracefully. NN4.7 just ignores the ones it doesn't support while IE5.0 exploits them.

But what are pseudo-classes? Let me cite the W3C on the definition of a pseudo-class:

Interactive user agents sometimes change the rendering in response to user actions. CSS provides three pseudo-classes for common cases:

• The :hover pseudo-class applies while the user designates an element (with some pointing device), but does not activate it. For example, a visual user agent could apply this pseudo-class when the cursor (mouse pointer) hovers over a box generated by the element. User agents not supporting interactive media do not have to support this pseudo-class. Some conforming user agents supporting interactive media may not be able to support this pseudo-class (e.g., a pen device).
• The :active pseudo-class applies while an element is being activated by the user. For example, between the times the user presses the mouse button and releases it.
• The :focus pseudo-class applies while an element has the focus (accepts keyboard events or other forms of text input).

These pseudo-classes are not mutually exclusive. An element may match several of them at the same time.

CSS doesn't define which elements may be in the above states, or how the states are entered and left. Scripting may change whether elements react to user events or not, and different devices and UAs may have different ways of pointing to, or activating elements.

User agents are not required to reflow a currently displayed document due to pseudo-class transitions. For instance, a style sheet may specify that the 'font-size' of an :active link should be larger than that of an inactive link, but since this may cause letters to change position when the reader selects the link, a UA may ignore the corresponding style rule.

Example(s):
A:link { color: red } /* unvisited links */
A:visited { color: blue } /* visited links */
A:hover { color: yellow } /* user hovers */
A:active { color: lime } /* active links */

So these dynamic pseudo-classes allow one, through the use of stylesheets, to make changes to elements with mouseovers without the use of JavaScript. Let's look at the style for a link that changes background color to red when the cursor passes over it.

a:hover {background:red;}

Below is the hover effect in action in IE5.0

we see in IE5.0 and NN6.0:

NN4.7 does not respond to this pseudo-class. If NN4.7 did, there wouldn't be the level of interest behind JavaScript rollovers.

Let's look at all of the pseudo-classes mentioned in the W3C cite above. Below is the code for a set of links.

<a href="index.html" title="mouseover me please">visited</a><br>
<a href="index1.html" title="mouseover me please">unvisited</a><br>
<a href="index1.html" title="mouseover me please">active</a><br>
<a href="index1.html" title="mouseover me please">hover</a><br>


Below is the style definitions for the A tag.

A:link { color: red } /* unvisited links */
A:visited { color: blue } /* visited links */
A:hover { color: yellow } /* user hovers */
A:active { color: lime } /* active links */


This is straight from the W3C source material above.

we see in NN4.7:	we see in IE50:

NN4.7 loses all the stylesheet link information. There are just visited and unvisited link colors, no hovered or active link colors are represented.

NN6.0 is a little odder. It doesn't respond to the UNVISITED color definition. The ACTIVE is a little odd. It's very difficult to make a link the active link and not actually chose it. If one clicks down on it and then moves off of the linkn, the link text background colors. If one left clicks someone else on the page, then the link text background will uncolor. If one right clicks someone else, the background color will more lightly color. It does respond to the HOVER definition as one would expect. NN6.0 does not respond at all to the TITLE attribute.