Use these methods to generate HTML tags programmatically when you can’t use a Builder. By default, they output XHTML compliant tags.

Methods
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E
T
Included Modules
Instance Public methods
cdata_section(content)

Returns a CDATA section with the given content. CDATA sections are used to escape blocks of text containing characters which would otherwise be recognized as markup. CDATA sections begin with the string <![CDATA[ and end with (and may not contain) the string ]]>.

cdata_section("<hello world>")
 # => <![CDATA[<hello world>]]>

Source: show 

# File rails/actionpack/lib/action_view/helpers/tag_helper.rb, line 65
def cdata_section(content)
  "<![CDATA[#{content}]]>"
end
content_tag(name, content_or_options_with_block = nil, options = nil, &block)

Returns an HTML block tag of type name surrounding the content. Add HTML attributes by passing an attributes hash to options. For attributes with no value like (disabled and readonly), give it a value of true in the options hash. You can use symbols or strings for the attribute names.

content_tag(:p, "Hello world!")
 # => <p>Hello world!</p>
content_tag(:div, content_tag(:p, "Hello world!"), :class => "strong")
 # => <div class="strong"><p>Hello world!</p></div>
content_tag("select", options, :multiple => true)
 # => <select multiple="multiple">...options...</select>

Instead of passing the content as an argument, you can also use a block in which case, you pass your options as the second parameter.

<% content_tag :div, :class => "strong" do -%>
  Hello world!
<% end -%>
 # => <div class="strong"><p>Hello world!</p></div>

Source: show 

# File rails/actionpack/lib/action_view/helpers/tag_helper.rb, line 47
def content_tag(name, content_or_options_with_block = nil, options = nil, &block)
  if block_given?
    options = content_or_options_with_block if content_or_options_with_block.is_a?(Hash)
    content = capture(&block)
    concat(content_tag_string(name, content, options), block.binding)
  else
    content = content_or_options_with_block
    content_tag_string(name, content, options)
  end
end
escape_once(html)

Returns the escaped html without affecting existing escaped entities.

escape_once("1 > 2 &amp; 3")
 # => "1 &lt; 2 &amp; 3"

Source: show 

# File rails/actionpack/lib/action_view/helpers/tag_helper.rb, line 73
def escape_once(html)
  fix_double_escape(html_escape(html.to_s))
end
tag(name, options = nil, open = false)

Returns an empty HTML tag of type name which by default is XHTML compliant. Setting open to true will create an open tag compatible with HTML 4.0 and below. Add HTML attributes by passing an attributes hash to options. For attributes with no value like (disabled and readonly), give it a value of true in the options hash. You can use symbols or strings for the attribute names.

tag("br")
 # => <br />
tag("br", nil, true)
 # => <br>
tag("input", { :type => 'text', :disabled => true }) 
 # => <input type="text" disabled="disabled" />

Source: show 

# File rails/actionpack/lib/action_view/helpers/tag_helper.rb, line 24
def tag(name, options = nil, open = false)
  "<#{name}#{tag_options(options) if options}" + (open ? ">" : " />")
end