HTML Post #4: Divs & Classes
Div Tags
A div tag is very similar to a paragraph tag. The difference from a rendering perspective is that paragraphs have a padding at the top and bottom by default. You can use div tags just like p tags.
Float Style
A div, and other tags, can have a float style. This can float the element on the left or the right. Here’s an example:
<div style="float: right">This floats on the right</div> <div style="float: left">This floats on the left</div> <div style="clear: both">This displays under the floats</div>
Yes, “clear: both” will clear all the floats above it. You can do “clear:left” to place is below the lowest left floating element. Float styles can be used with images as well.
CSS Classes
Styles can be declared once and referred using the class attribute. These styles can be declared using a stylesheet file or a style element. A stylesheet is better because it can be used by multiple pages by adding one line inside the html header:
<link rel="stylesheet" type="text/css" href="http://example.com/main.css" />
If you want to just play a little bit, you can put a style section in the html header:
<style type="text/css"> /* This is a style comment. */ /* Put your stylesheet here in the html header! */ </style>
You can take this:
<div style="float: left; color: red;">Red Left</div> <div style="float: left; color: red;">Red Left</div> <div style="float: left; color: red;">Red Left</div> <div style="float: left; color: red;">Red Left</div>
And turn it into this:
<style type="text/css">
.left-red { float: left; color: red; }
</style>
...
<div class="left-red">Red Left</div>
<div class="left-red">Red Left</div>
<div class="left-red">Red Left</div>
<div class="left-red">Red Left</div>
Note that the class in the style starts with a period and in the div doesn’t. This is because you are telling the browser that left-red is a class. If it started with a letter, the browser would think it was an element, like a “div” tag. Also, curly braces surround what would be in the style attribute.
Now, go play around for 30 minutes with some html. If you have a question, feel free to ask.
- HTML Post #1
- HTML Post #2: Lists & Links
- HTML Post #3: Images
- HTML Post #4: Divs & Classes
- HTML Post #5: Tables & Whitespace
- HTML Post #6: Forms
- HTML Post #7: CSS & Browsers
HTML Post #3: Images
Image Tag
<img src="http://example.com/image.jpg" alt="Example Image" />
That will give you just an image, plain and simple. The alt tag is important for people who have images disabled and for search engines. Here’s how to center or left align an image:
<img src="http://example.com/image.jpg" alt="Centered Image" align="center" /> <img src="http://example.com/image.jpg" alt="Left Aligned Image" align="left" />
When using an image inside a link, there will be an automatic blue broder. To remove this:
<a href="http://example.com/"> <img src="http://example.com/images.jpg" alt="Link Image" border="0" /> </a>
Background Images
We’ve all seen images used as backgrounds. It’s fairly simple. To put a background image for the whole page, change the opening body tag to this:
<body style="background: url('image.jpg');">
You can change the repeat by adding the repeat-y keyword like this:
<body style="background: url('image.jpg') repeat-y;">
The image will fill the page top to bottom, but not left to right. There are plenty of options for you background image. Here are the repeats:
- repeat — tiled to fill completely (default)
- repeat-y — repeats top to bottom
- repeat-x — repeats left to right
- no-repeat — does not repeat
You can also make it scroll with the page or fixed to the screen and does not scroll. Scroll is the default.
You can also set the background of a p, or paragraph, tag the same way.
<p style="background: url('image2.jpg');">I've got a background image!</p>
The full image will not show if there is not enough text.
Colors
You can set the background color, similarly to using an image:
<p style="background-color: red;">I've got a background color!</p> <p style="background-color: red; color: yellow;">I've got a foreground color!</p>
In the second example, the text will be yellow on red, while the first is black on red.
- HTML Post #1
- HTML Post #2: Lists & Links
- HTML Post #3: Images
- HTML Post #4: Divs & Classes
- HTML Post #5: Tables & Whitespace
- HTML Post #6: Forms
- HTML Post #7: CSS & Browsers
HTML Post #2: Lists & Links
Lists
There are two basic types of lists in HTML: ordered and unordered. Unordered lists are bullet lists. Ordered lists are numbered. Each item in the list is housed in between opening and closing “li” tags.
Ordered Lists
A simple numbered list is surrounded by opening and closing “ol” tags. Here is a quick example:
<ol> <li>Step 1.</li> <li>Step 2.</li> </ol>
This looks like:
- Step 1.
- Step 2.
You can use a different marker, just as lowercase letters, uppercase letters, and roman numerals. This is done by styling the list. Here’s how to do roman numerals:
<ol style="list-style-type: upper-roman"> <li>Step I.</li> <li>Step II.</li> </ol>
- Step I.
- Step II.
Here are the different ordered list style types:
| upper-letter | Uppercase Letters |
| lower-letter | Lowercase Letters |
| upper-roman | Uppercase Roman Numerals |
| lower-roman | Lowercase Roman Numerals |
| upper-greek | Uppercase Greek Letters |
| lower-greek | Lowercase Greek Letters |
| decimal | Regular Numbers |
| decimal-leading-zero | Leading Zero |
Unordered Lists
These are almost identical to ordered lists. Instead of “ol”, you use “ul”. The default list style type is a bullet. Here are the unordered types:
- none
- circle
- disc
- square
Here’s that unordered list in HTML:
<ul> <li>none</li> <li>circle</li> <li>disc</li> <li>square</li> </ul>
Links
A link is super easy to do. It’s an “a” tag. The tag has an “href” attribute that contains the url, just like the “style” attribute contained the styling information. Here’s a quick example:
<a href="http://example.com/">Example.com</a>
Which would like like:
You can also tell the browser to open the link in a new window/tab by using the “target” attribute:
<a href="http://example.com/" target="_blank">Example.com in a new window/tab</a>
Example.com in a new window/tab
You can even style the “a” tag to set the color and remove the underline:
<a href="http://example.com/some_web_page.html" style="color: black; text-decoration: none">Example.com</a>
Yes, you can set the color of any text with that style attribute. Also note that multiple styles are separated by a semicolon, and it does not matter the order of the styling when put in the “style” attribute, so long as there’s nothing conflicting.
Well, that’s pretty much it for lists & links. The next post is all about images, so check back!
- HTML Post #1
- HTML Post #2: Lists & Links
- HTML Post #3: Images
- HTML Post #4: Divs & Classes
- HTML Post #5: Tables & Whitespace
- HTML Post #6: Forms
- HTML Post #7: CSS & Browsers
HTML Post #1
More and more people are starting their own websites. Whether it be a blog, an e-commerce site, or a tribute to their pet, learning HTML will help tremendously. Sure, there are those nice little editors, but they cannot do everything. Plus, sometimes you’ll want to tweak that HTML so everything displays properly. In this series, I’ll cover the basics of a webpage, images, tables, lists, styles, and some other topics.
Base Document
I have setup a base HTML document to show the basics that will be covered in this series. You can find it here. It contains a lot of comments which are ignored by the web browser. An HTML comment starts with “<!–” and ends with “–>”, quotes for clarity.
HTML Tags
Tags are special markers that tell the web browser how to display the page. Tags always start with a less than symbol “<” and end with a greater than symbol “>”. There are three types of tags: opening, closing, and self-closing. Closing tags start with “</”. Self-closing tags end with “/>”. Every opening tag should have a closing tag. An HTML document will display everything between the “<body>” opening tag and “</body>” closing tag.
DOCTYPE
All HTML documents should start with a DOCTYPE tag. This tag tells the browser which version of HTML you are using and determines how it will render the page. There are serveral different doctypes, but for this series, we’ll be using XHTML Strict.
Basic Tags
The basic tags are:
- html
This should open immediately after the doctype and close at the very end of the file. - head
This follows the opening html tag. It contains the title, meta data, and links to stylesheet and javascript files. - body
This follows the closing head tag. Its contents will display as the webpage. Update: Javascript should be placed as close to the end of the bottom as possible. - title
This contains the title of the page, it shows in the tab and/or the titlebar of the browser. - p
This is a paragraph. Each paragraph will have a bit of whitespace before and after them. - b
This bolds the text between the opening and closing b tag.
Sample
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html> <head> <title>This is just a sample</title> </head> <body> <p>This is a paragraph.</p> <p><b>This is a bold paragraph.</b></p> <p>There is only <b>one</b> word bold in this paragraph.</p> <p>It is <b>important</b> to close tags in <b>reverse</b> order they were <b>opened.</b></p> </body> </html>
- HTML Post #1
- HTML Post #2: Lists & Links
- HTML Post #3: Images
- HTML Post #4: Divs & Classes
- HTML Post #5: Tables & Whitespace
- HTML Post #6: Forms
- HTML Post #7: CSS & Browsers
Is GHz per Watt the new measure?
We have reached a plateau when it comes to speed limits for CPUs. We may not see anything higher than 4 GHz in the near future. This doesn’t mean that the computer can’t be better or faster. Multicore processors are fairly common today, allowing more than one section of code to run simultaneously. Computers are also dropping their power requirements, and let’s face it, we all want to be green, especially if it means a small electricity bill and keeping some green in our pocket.
Chip manufacturers are now touting about their CPU’s power consumption. Laptops are where this is the major selling point. Less electricity used means a longer battery life. Also, if it can do the same amount of data processing, you can have the same level of productivity for a longer amount of time. Wouldn’t we all want a laptop that can play 4 flash movies and not stutter a single one?
The desktop market hasn’t seen anything to the point of GHz/Watt. That’s because the folks in marketing think no one really cares how much electricity that computer’s going to use, unless you’re a computer dork like me running around the house with your brand new kill-a-watt. I found an article on Wikipedia, they’ve listed pretty much every known CPU, their power requirements, speed and MHz/Watt or GHz/Watt.
Sure, there’s more to that computer than a CPU. There’s RAM, a hard drive, monitor, keyboard, mouse, USB ports and devices, network connections, fans, and other chips to support everything from video to audio to that fancy SATA II interface blu-ray burner you just had installed. Where are the power requirements, in Watts, for all these devices? Can it be found? Is it even available?
If the data can be found, could a normal high school graduate understand it? Would they even care? I’m betting most people won’t.
