They have the same effect on normal web browser rendering engines, but there is a fundamental difference between them.
As the author writes in a discussion list post:
Think of three different situations:
- web browsers
- blind people
- mobile phones
"Bold" is a style - when you say "bold a word", people basically know that
it means to add more, let's say "ink", around the letters until they stand out
more amongst the rest of the letters.
That, unfortunately, means nothing to a blind person. On mobile phones
and other PDAs, text is already bold because screen resolution is very small. You can't bold a bold without screwing something up.
<b>
is a style - we know what "bold" is supposed to look like.
<strong>
however is an indication of how something should be understood. "Strong" could (and often does) mean "bold" in a browser, but it could also mean a lower tone for a speaking program like Jaws (for blind people) or be represented by an underline (since you can't bold a bold) on a Palm Pilot.
HTML was never meant to be about styles. Do some searches for "Tim Berners-Lee" and "the semantic web." <strong>
is semantic—it describes the text it surrounds (e.g., "this text should be stronger than the rest of the text you've displayed") as opposed to describing how the text it surrounds should be displayed (e.g., "this text should be bold").
Basics
For controlling "cellpadding" in CSS, you can simply use padding
on table cells. E.g. for 10px of "cellpadding":
td {
padding: 10px;
}
For "cellspacing", you can apply the border-spacing
CSS property to your table. E.g. for 10px of "cellspacing":
table {
border-spacing: 10px;
border-collapse: separate;
}
This property will even allow separate horizontal and vertical spacing, something you couldn't do with old-school "cellspacing".
Issues in IE ≤ 7
This will work in almost all popular browsers except for Internet Explorer up through Internet Explorer 7, where you're almost out of luck. I say "almost" because these browsers still support the border-collapse
property, which merges the borders of adjoining table cells. If you're trying to eliminate cellspacing (that is, cellspacing="0"
) then border-collapse:collapse
should have the same effect: no space between table cells. This support is buggy, though, as it does not override an existing cellspacing
HTML attribute on the table element.
In short: for non-Internet Explorer 5-7 browsers, border-spacing
handles you. For Internet Explorer, if your situation is just right (you want 0 cellspacing and your table doesn't have it defined already), you can use border-collapse:collapse
.
table {
border-spacing: 0;
border-collapse: collapse;
}
Note: For a great overview of CSS properties that one can apply to tables and for which browsers, see this fantastic Quirksmode page.
Best Answer
Meet the Units
Pixels (px): Pixels are fixed-size units that are used in screen media (i.e. to be read on the computer screen). One pixel is equal to one dot on the computer screen (the smallest division of your screen’s resolution). Many web designers use pixel units in web documents in order to produce a pixel-perfect representation of their site as it is rendered in the browser. One problem with the pixel unit is that it does not scale upward for visually-impaired readers or downward to fit mobile devices.
Points (pt): Points are traditionally used in print media (anything that is to be printed on paper, etc.). One point is equal to 1/72 of an inch. Points are much like pixels, in that they are fixed-size units and cannot scale in size.
Percent (%): The percent unit is much like the “em” unit, save for a few fundamental differences. First and foremost, the current font-size is equal to 100% (i.e. 12pt = 100%). While using the percent unit, your text remains fully scalable for mobile devices and for accessibility.
So, What’s the Difference?
It’s easy to understand the difference between font-size units when you see them in action. Generally, 1em = 12pt = 16px = 100%. When using these font-sizes, let’s see what happens when you increase the base font size (using the body CSS selector) from 100% to 120%
As you can see, both the em and percent units get larger as the base font-size increases, but pixels and points do not. It can be easy to set an absolute size for your text, but it’s much easier on your visitors to use scalable text that can display on any device or any machine. For this reason, the em and percent units are preferred for web document text.
Em vs. Percent
We’ve decided that point and pixel units are not necessarily best suited for web documents, which leaves us with the em and percent units. In theory, both the em and the percent units are identical, but in application, they actually have a few minor differences that are important to consider.
In the example above, we used the percent unit as our base font-size (on the body tag). If you change your base font-size from percent to ems (i.e. body { font-size: 1em; }), you probably won’t notice a difference. Let’s see what happens when “1em” is our body font-size, and when the client alters the “Text Size” setting of their browser (this is available in some browsers, such as Internet Explorer).
When the client’s browser text size is set to “medium,” there is no difference between ems and percent. When the setting is altered, however, the difference is quite large. On the “Smallest” setting, ems are much smaller than percent, and when on the “Largest” setting, it’s quite the opposite, with ems displaying much larger than percent. While some could argue that the em units are scaling as they are truly intended, in practical application, the em text scales too abruptly, with the smallest text becoming hardly legible on some client machines.
Info taken from http://kyleschaeffer.com