I needed to make sure that an element is visible and not overshadowed by an element that has a higher z-index (like a modal overlay).

Here is the step I wanted:

Then the very important notice should not be overshadowed by another element

This is the step definition:

```
Then(/^(.*?) should not be overshadowed by another element$/) do |locator|
selector = selector_for(locator)
expect(page).to have_css(selector)
js = «-JS
var selector = #{selector.to_json};
var elementFromSelector = document.querySelector(selector)…

Our applications not only need to be functional, they need to be fast.

But, to quote Donald Knuth,

premature optimization is the root of all evil (or at least most of it) in programming

The reasoning is that you should not waste your time optimizing code where it does not even matter. However, I believe there are some kinds of optimizations you should do right away, because

• they are either obvious and easy
• or they are very hard to do optimize later

This is an attempt to list some of those things:

On the server

…

This is useful if, for example, you want to use a background-image that has to scale with the width and the div should only have the height of the picture.

html:

<div class="outer">
  <div class="inner">
  </div>
</div>

css:

.outer {
  width: 100%;
  background-image: image-url('background.png');
  background-size: cover;
}
  
.inner {
  padding-top: 60%;
}

How does it work?

There are several CSS attributes that can handle values as percentage. But they use different other attributes as "reference value…

Middleman is a static page generator that brings many of the goodies that Rails developers are used to.

Out of the box, Middleman brings Haml, Sass, helpers etc. However, it can be configured to do even better. This card is a list of improvement hints for a Rails developer.

Gemfile

Remove tzinfo-data and wdm unless you're on Windows. Add these gems:

```
gem 'middleman-livereload'
gem 'middleman-sprockets' # Asset pipeline!

gem 'bootstrap-sass' # If you want to use Bootstrap

gem 'byebug'

gem 'capistrano'
gem 'capistrano-mid…

Just dumping this in case somebody might need it.

When you need a CSS value (a padding, margin, height etc) to shrink/grow proportionally with the parent element, you normally use percentage values. However, if you need specific values at two given widths, you need to turn to linear functions. The mixin below gives you just that.

```
// Call with two desired values at two different widths.
// Returns a calc() expression that will scale proportionally between those two.
// Example:
// Spaci…

As the web is being used for more and more tasks, expectations rise. Not only should web pages offer rich interaction, they must be responsive in both size and interaction.

This imposes a paradoxon that needs to be solved by building performing applications. It's not enough any more to have your web site do crazy stuff, it is also required to do it crazy fast. This card is intended to give you an introduction to this emerging aspect of web development.

Read this introductory [performance study on Pinterest](http://www.smashingmagazine.com/…

TLDR: When you put CSS rules into a partial and import that partial multiple times, the CSS rules will be duplicated in the compiled CSS.

Here is a Sass partial called _fonts.sass that contains both CSS rules and a mixin:

@font-face
  font-family: SuperType
  src: url('supertype.woff')
  
=title-font
  font-family: SuperType

This _fonts.sass is not practical in CSS projects that are organized over multiple files: When you…

SVG is an acronym for "scalable vector graphics". SVGs should be used whenever an image can be described with vector instructions like "draw a line there" or "fill that space" (they're not suited for photographs and the like). Benefits are the MUCH smaller file size and the crisp and sharp rendering at any scale.

It's a simple, old concept brought to the web – half-heartedly. While actually all browsers pretend to support SVG, some barely complex use cases get you beyond common browser support.

In the bas…