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穿越火线4+1 www.yfq3.com The default grid system provided as part of Bootstrap is a 940px-wide, 12-column grid.

It also has four responsive variations for various devices and resolutions: phone, tablet portrait, table landscape and small desktops, and large widescreen desktops.

<div class="row">
  <div class="span4">...</div>
  <div class="span8">...</div>
</div>

As shown here, a basic layout can be created with two "columns," each spanning a number of the 12 foundational columns we defined as part of our grid system.


Offsetting columns

4
4 offset 4
3 offset 3
3 offset 3
8 offset 4
<div class="row">
  <div class="span4">...</div>
  <div class="span4 offset4">...</div>
</div>

Nesting columns

With the static (non-fluid) grid system in Bootstrap, nesting is easy. To nest your content, just add a new .row and set of .span* columns within an existing .span* column.

Example

Nested rows should include a set of columns that add up to the number of columns of it's parent. For example, two nested .span3 columns should be placed within a .span6.

Level 1 of column
Level 2
Level 2
<div class="row">
  <div class="span12">
    Level 1 of column
    <div class="row">
      <div class="span6">Level 2</div>
      <div class="span6">Level 2</div>
    </div>
  </div>
</div>

Fluid columns

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Percents, not pixels

The fluid grid system uses percents for column widths instead of fixed pixels. It also has the same responsive variations as our fixed grid system, ensuring proper proportions for key screen resolutions and devices.

Fluid rows

Make any row fluid simply by changing .row to .row-fluid. The columns stay the exact same, making it super straightforward to flip between fixed and fluid layouts.

Markup

<div class="row-fluid">
  <div class="span4">...</div>
  <div class="span8">...</div>
</div>

Fluid nesting

Nesting with fluid grids is a bit different: the number of nested columns doesn't need to match the parent. Instead, your columns are reset at each level because each row takes up 100% of the parent column.

Fluid 12
Fluid 6
Fluid 6
<div class="row-fluid">
  <div class="span12">
    Level 1 of column
    <div class="row-fluid">
      <div class="span6">Level 2</div>
      <div class="span6">Level 2</div>
    </div>
  </div>
</div>
Variable Default value Description
@gridColumns 12 Number of columns
@gridColumnWidth 60px Width of each column
@gridGutterWidth 20px Negative space between columns
@siteWidth Computed sum of all columns and gutters Counts number of columns and gutters to set width of the .container-fixed() mixin

Variables in LESS

Built into Bootstrap are a handful of variables for customizing the default 940px grid system, documented above. All variables for the grid are stored in variables.less.

How to customize

Modifying the grid means changing the three @grid* variables and recompiling Bootstrap. Change the grid variables in variables.less and use one of the four ways documented to recompile. If you're adding more columns, be sure to add the CSS for those in grid.less.

Staying responsive

Customization of the grid only works at the default level, the 940px grid. To maintain the responsive aspects of Bootstrap, you'll also have to customize the grids in responsive.less.

Fixed layout

The default and simple 940px-wide, centered layout for just about any website or page provided by a single <div class="container">.

<body>
  <div class="container">
    ...
  </div>
</body>

Fluid layout

<div class="container-fluid"> gives flexible page structure, min- and max-widths, and a left-hand sidebar. It's great for apps and docs.

<div class="container-fluid">
  <div class="row-fluid">
    <div class="span2">
      <!--Sidebar content-->
    </div>
    <div class="span10">
      <!--Body content-->
    </div>
  </div>
</div>

Responsive devices

What they do

Media queries allow for custom CSS based on a number of conditions—ratios, widths, display type, etc—but usually focuses around min-width and max-width.

  • Modify the width of column in our grid
  • Stack elements instead of float wherever necessary
  • Resize headings and text to be more appropriate for devices

Use media queries responsibly and only as a start to your mobile audiences. For larger projects, do consider dedicated code bases and not layers of media queries.

Supported devices

Bootstrap supports a handful of media queries in a single file to help make your projects more appropriate on different devices and screen resolutions. Here's what's included:

Label Layout width Column width Gutter width
Smartphones 480px and below Fluid columns, no fixed widths
Smartphones to tablets 767px and below Fluid columns, no fixed widths
Portrait tablets 768px and above 42px 20px
Default 980px and up 60px 20px
Large display 1200px and up 70px 30px

Requires meta tag

To ensure devices display responsive pages properly, include the viewport meta tag.

<meta name="viewport" content="width=device-width, initial-scale=1.0">

Using the media queries

Bootstrap doesn't automatically include these media queries, but understanding and adding them is very easy and requires minimal setup. You have a few options for including the responsive features of Bootstrap:

  1. Use the compiled responsive version, bootstrap-responsive.css
  2. Add @import "responsive.less" and recompile Bootstrap
  3. Modify and recompile responsive.less as a separate file

Why not just include it? Truth be told, not everything needs to be responsive. Instead of encouraging developers to remove this feature, we figure it best to enable it.

// Landscape phones and down
@media (max-width: 480px) { ... }

// Landscape phone to portrait tablet
@media (max-width: 768px) { ... }

// Portrait tablet to landscape and desktop
@media (min-width: 768px) and (max-width: 980px) { ... }

// Large desktop
@media (min-width: 1200px) { .. }

Responsive utility classes

What are they

For faster mobile-friendly development, use these basic utility classes for showing and hidding content by device.

When to use

Use on a limited basis and avoid creating entirely different versions of the same site. Instead, use them to complement each device's presentation.

For example, you might show a <select> element for nav on mobile layouts, but not on tablets or desktops.

Support classes

Shown here is a table of the classes we support and their effect on a given media query layout (labeled by device). They can be found in responsive.less.

Class Phones 480px and below Tablets 767px and below Desktops 768px and above
.visible-phone Visible
.visible-tablet Visible
.visible-desktop Visible
.hidden-phone Visible Visible
.hidden-tablet Visible Visible
.hidden-desktop Visible Visible

Test case

Resize your browser or load on different devices to test the above clases.

Visible on...

  • Phone✔ Phone
  • Tablet✔ Tablet
  • Desktop✔ Desktop

Hidden on...

  • Phone✔ Phone
  • Tablet✔ Tablet
  • Desktop✔ Desktop
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