In front of some attention to the problem

(1) If you do not set the height of your parent box, the parent box will be propped up with what you write in the parent box.

(2) If the parent box in which the height is set, but you give the child box to set the float, which the parent box will not be stretched (because the child box itself will deviate from the document flow, so that the result)

(3) Special use of pseudo class:

#four {
width:200px;
height:200px;
background:red;
}
#four: after{
Content: "";
Display:block;
width:20px;
height:20px;
Background:yellow;
}

Do you know. Here you will have a small box with a long width of 20px on the left upper foot of the box with the ID four you set up. If you want to reset the location of the small box, here is the need to set the parent box reltive, to which the child box with the Psition attribute, Here you can make a new arrangement for the location.

(3) The difference between get and post in http:

Get: Fetching data from a specified server

Post: Submit data to the specified server

        Get method: When using the Getting method, the query string (the key value pair) is appended to the server together with the URL address:/test/demo_form.jsp?name1=value1& Name2=value2 feature: Get request can be cached by cache Get request can be saved in browser's browsing record with the URL that gets requested can be saved as browser bookmark a GET request has a length limit getting request is used primarily to obtain the data post method: When using the Post method, The query string exists separately in POST information and is sent to the server along with the HTTP request: post/test/demo_form.jsp http/1.1 Host:w3schools.com name1=value1&name2= Value2 Features: Post requests cannot be cached post requests are not saved in browser browsing records the URL of a POST request cannot be saved as a browser bookmark the difference between get and post is not limited by the length of the POST request:

	get	POST
Click return/Refresh button	no effect	data will be sent again (the browser will prompt the user "data is resubmitted")
Add bookmark	can	no
Cache	can	can not
encoding type (Encoding type)	application/x- www-form-urlencoded	application/x-www-form-urlencoded or multipart/form-data. Please use multipart encoding for binary data
History	has	no
length limit	have	no
data type limit	allow only ASCII character types	is not restricted. Allow binary data
security	The query string appears in the URL of the address bar and is not secure, do not use GET requests to submit sensitive data	because the data will not appear in the address bar, nor Cached or saved in a browsing record, it is not the safest way to see a post plea than GET request security. If you need to transfer sensitive data, use encryption to transfer the
Visibility	query string displayed in the URL of the address bar, visible	query string will not appear in the Address bar, not visible

Other HTTP request methods

Way	Describe
Head	Similar to get request, different in the server only return HTTP header information, no page content
Put	Upload a description of the specified URL
DELETE	Delete specified resource
OPTIONS	Returns the HTTP method supported by the server
CONNECT	Connection requests converted to transparent TCP/IP tunnels

(4) The abbr here is to add a underline to the corresponding text or to add the next stroke.

(5) Define a list of its own:

The original form is:

<dl>

<dd></dd>

<dt></dt>

</dl>

Where the DL is the defined list element

Where the DD is represented here is the definition of the header element

Its total dt is here to define the description element

(6) in the JS array of

The array subscript in 1.js is not necessarily a number, and JS can use the string as the subscript for the array.

An array of 2.js does not necessarily require his length at the time of the Declaration.

3 in JS and the array elements can not be the same type, and the array element can also be a variable, the value of an array element can also be an element of another array, the array can also contain other arrays

4. Even if the length of the array is specified, the array is still continuously variable, that is, even if the length of the array is defined, the element can be stored outside the length of the array (the length of which will change itself)

5 addition of array elements:

"1. Arrayobj. Push ([Item1 [item2 [...] [Itemn]]]); /Adds one or more new elements to the end of the array and returns the new length of the array

"2. Arrayobj.unshift ([Item1 [item2 [...] [Itemn]]]); /Adds one or more new elements to the beginning of the array, the elements in the array are automatically moved back, and the new length of the array is returned

"3. Arrayobj.splice (insertpos,0,[item1[, item2[, ...) [, Itemn]]]); /inserts one or more new elements into the array at the specified position, and the element at the insertion point is automatically moved back to "".

Here it is necessary to study the addition of elements in the specified location of the array:

2 3 4 5 6

The original array var array = ["One", "two", "four"]; Splice (position, Numberofitemstoremove, item)