Responsive design with media query : screen size?

Question 1

Responsive Web design (RWD) is a Web design approach aimed at crafting sites to provide an optimal viewing experience

When you design your responsive website you should consider the size of the screen and not the device type. The media queries helps you do that.

If you want to style your site per device, you can use the user agent value, but this is not recommended since you'll have to work hard to maintain your code for new devices, new browsers, browsers versions etc while when using the screen size, all of this does not matter.

You can see some standard resolutions in this link.

BUT, in my opinion, you should first design your website layout, and only then adjust it with media queries to fit possible screen sizes.

Why? As I said before, the screen resolutions variety is big and if you'll design a mobile version that is targeted to 320px your site won't be optimized to 350px screens or 400px screens.

TIPS

When designing a responsive page, open it in your desktop browser and change the width of the browser to see how the width of the screen affects your layout and style.
Use percentage instead of pixels, it will make your work easier.

Example

I have a table with 5 columns. The data looks good when the screen size is bigger than 600px so I add a breakpoint at 600px and hides 1 less important column when the screen size is smaller. Devices with big screens such as desktops and tablets will display all the data, while mobile phones with small screens will display part of the data.

State of mind

Not directly related to the question but important aspect in responsive design. Responsive design also relate to the fact that the user have a different state of mind when using a mobile phone or a desktop. For example, when you open your bank's site in the evening and check your stocks you want as much data on the screen. When you open the same page in the your lunch break your probably want to see few important details and not all the graphs of last year.

Question 2

Here is media queries for common device breakpoints.

    /* Smartphones (portrait and landscape) ----------- */
@media only screen and (min-device-width : 320px) and (max-device-width : 480px) {
/* Styles */
}

/* Smartphones (landscape) ----------- */
@media only screen and (min-width : 321px) {
/* Styles */
}

/* Smartphones (portrait) ----------- */
@media only screen and (max-width : 320px) {
/* Styles */
}

/* iPads (portrait and landscape) ----------- */
@media only screen and (min-device-width : 768px) and (max-device-width : 1024px) {
/* Styles */
}

/* iPads (landscape) ----------- */
@media only screen and (min-device-width : 768px) and (max-device-width : 1024px) and (orientation : landscape) {
/* Styles */
}

/* iPads (portrait) ----------- */
@media only screen and (min-device-width : 768px) and (max-device-width : 1024px) and (orientation : portrait) {
/* Styles */
}
/**********
iPad 3
**********/
@media only screen and (min-device-width : 768px) and (max-device-width : 1024px) and (orientation : landscape) and (-webkit-min-device-pixel-ratio : 2) {
/* Styles */
}

@media only screen and (min-device-width : 768px) and (max-device-width : 1024px) and (orientation : portrait) and (-webkit-min-device-pixel-ratio : 2) {
/* Styles */
}
/* Desktops and laptops ----------- */
@media only screen  and (min-width : 1224px) {
/* Styles */
}

/* Large screens ----------- */
@media only screen  and (min-width : 1824px) {
/* Styles */
}

/* iPhone 4 ----------- */
@media only screen and (min-device-width : 320px) and (max-device-width : 480px) and (orientation : landscape) and (-webkit-min-device-pixel-ratio : 2) {
/* Styles */
}

@media only screen and (min-device-width : 320px) and (max-device-width : 480px) and (orientation : portrait) and (-webkit-min-device-pixel-ratio : 2) {
/* Styles */
}

Question 3

The screen widths Bootstrap v3.x uses are as follows:

Extra small devices Phones (<768px) / .col-xs-
Small devices Tablets (≥768px) / .col-sm-
Medium devices Desktops (≥992px) / .col-md-
Large devices Desktops (≥1200px) / .col-lg-

So, these are good to use and work well in practice.

Question 4

Take a look at this... http://getbootstrap.com/

For big websites I use Bootstrap and sometimes (for simple websites) I create all the style with some @mediaqueries. It's very simple, just think all the code in percentage.

.container {
max-width: 1200px;
width: 100%;
margin: 0 auto;
}

Inside the container, your structure must have widths in percentage like this...

.col-1 {
width: 40%;
float: left;
}

.col-2 {
width: 60%;
float: left;
}

@media screen and (max-width: 320px) {
.col-1, .col-2 { width: 100%; }
}

In some simple interfaces, if you start to develop the project in this way, you will have great chances to have a fully responsive site using break points only to adjust the flow of objects.

Question 5

i will provide mine because @muni s solution was a bit overkill for me

note: if you want to add custom definitions for several resolutions together, say something like this:

//mobile generally   
 @media screen and (max-width: 1199)  {

      .irns-desktop{
        display: none;
      }

      .irns-mobile{
        display: initial;
      }

    }

Be sure to add those definitions on top of the accurate definitions, so it cascades correctly (e.g. 'smartphone portrait' must win versus 'mobile generally')

//here all definitions to apply globally


//desktop
@media only screen
and (min-width : 1200) {


}

//tablet landscape
@media screen and (min-width: 1024px) and (max-width: 1600px)  {

} // end media query

//tablet portrait
@media screen and (min-width: 768px) and (max-width: 1023px)  {

}//end media definition


//smartphone landscape
@media screen and (min-width: 480px) and (max-width: 767px)  {

}//end media query



//smartphone portrait
@media screen /*and (min-width: 320px)*/
and (max-width: 479px) {

}

//end media query