CSS Techniques I Wish I Knew When I Started Designing Websites

By Tim Wright and TJ Kelly

CSS is the best thing to happen to the web since Tim Berners-Lee. It’s simple, powerful, and easy to use. But even with all its simplicity, it hides some important capabilities. Ask any designer, and they’ll tell you that the majority of their code headaches are caused and ultimately solved by CSS.

All designers at some point in their career go through the process of encountering a weird display issue, searching for a resolution, and discovering a trick, technique, or hack could have saved them hours of frustration—if they had only known when they started.

We’ve put together a list of the most frustrating and time-consuming CSS headaches and, more importantly, their solutions (along with examples and further resources). I hope this list will help you save some gray hairs. As for me, I think I feel some coming in right now…

Resets & Browser Inconsistencies

Not all browsers are created equal. In fact, every browser is different. What is the default margin, padding, or font-size of a 

 element? You might be surprised at the wide range of values. To handle the differences between browsers, many of us want to level the playing field and start from scratch, by using CSS reset styles.

The early stages of resets, designers dealt with differing margin and padding values, using a global reset:

* { margin: 0; padding: 0; }

But, as more people used and discussed resets, it became clear that resetting only margin & padding wasn’t enough (and, applying the above rule to every element is taxing on the rendering engine). Thanks to the work of Eric Meyer and other CSS pioneers, a better, more complete collection of reset rules was created:

html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, font, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td {
 margin: 0;
 padding: 0;
 border: 0;
 outline: 0;
 font-weight: inherit;
 font-style: inherit;
 font-size: 100%;
 font-family: inherit;
 vertical-align: baseline;
 }
/* remember to define focus styles! */
:focus {
 outline: 0;
 }
body {
 line-height: 1;
 color: black;
 background: white;
 }
ol, ul {
 list-style: none;
 }
/* tables still need 'cellspacing="0"' in the markup */
table {
 border-collapse: separate;
 border-spacing: 0;
 }
caption, th, td {
 text-align: left;
 font-weight: normal;
 }
blockquote:before, blockquote:after,
q:before, q:after {
 content: "";
 }
blockquote, q {
 quotes: "" "";
 }

As important as it is to note which elements are included in the most popular CSS reset available today .It’s also important to note some of the elements that are deliberately excluded from this list:

• input
• button
• hr

These elements were excluded because their cross-browser differences are so vast that you would have to completely unstyle them to create a "bulletproof" element. They’re so weird, that even then, there’s no guarantee.

Resources for Resets

• Eric Meyer’s Resets and the reasoning behind them
• Smashing article: “Design from Scratch”
• Google BluePrint CSS & Resets
• Yahoo YUI CSS Resets

Box Model — Margin, Padding & Borders

The box model is the basis for all layouts. It governs the dimensions & spacing of the elements on a page. To understand it, we have to understand the difference betweenblock-level elements and inline elements.

Block-level elements, by default, take up the entire width of their containing element and the height of the default line-height. They will stack up underneath each other, top-to-bottom. Therefore, by default, they will take up their own line on a page. Some block-level elements are: 

, 

, , 
, 
, 
, etc.

Inline elements are, just as their name implies, in-line. They will stack up next to each other, left-to-right. When given content, they will take up the exact width and height of that content. Given no content, they will collapse down and have no width or height. Some in-line elements are: , , , , , etc.

All HTML block-level elements have five spacing properties: height, width, margin,padding, and border (inline elements have them too, they just work a bit differently). Width and height are tricky attributes, as they require a bit of calculation. When measuring an element’s width, designers must consider the entire box.

In the example below, the box has a total width of 260px. The margin, padding, and border are 30px each (remember, that’s 30px on top, 30 on bottom, 30 right, and 30 left). So, in this example, the margin takes up 60 pixels of the box’s width. Likewise, the border and padding consume 60px each. All together, the margin, border, and padding amount to 180 pixels of the box’s total width.



We know that the box’s total width is 260px, but in CSS the width attribute refers to thecontent area on the inside of the box. So, for this example, we have to subtract 180 pixels (for margin, border, and padding) from 260 (total box width), leaving us with a content area of 80px. Therefore, our CSS looks like this:

div {
  margin:30px;
  border:30px solid yellow;
  padding:30px;
  width:80px;
  height:80px;
}
Extras
All of the examples and rules we’re discussed for the width property also apply to height.
margin can support negative values. Use them cautiously but they can prove to be very strong design elements.
Don’t forget the units with the box model. Only a zero-value (margin:0;) can be written without a unit specified.
Resources for CSS Box Model

W3C CSS Specifications
HTMLsource Box Model tutorial by Ross Shannon
“Beginner’s Guide to Margins and Paddings” at Web Designer Notebook
Dimensions — Width, Height, Min & Max
Now that we understand how to use width and height in unison with the box model, let’s look at some of the flexibility of CSS dimensions. Modern browsers support min- and max-width (and the same for height), allowing us to get creative with dimensions and create flexible layouts.

Width/height specify the space an object should occupy. They can be measured in pixels (10px), ems (10em) and percentages (10%), as well as a few other units. Defining a width or height for an element will force that element to keep those dimensions, regardless of the content inside it. So, if our content is too big for its container, it will be cut off, hiding the bottom of our content (or just look really messed up).

Min-width & min-height
Giving an element a min-width or min-height will set the element to our exact dimension by default. But, since we only provided a minimum dimension, as the content grows, the containing element will allowed to stretch and all of our content will remain visible.

Min-width & min-height can he useful for form elements like  and