Web Standards FAQ Collection 3_ Experience Exchange

What is the difference between the definition ID and class in the 10.web standard?
<textarea id="runcode54285"><! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 strict//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" > < Meta http-equiv= "Content-type" content= "text/html; charset=gb2312 "/> <style type=" Text/css "> <!--#aa {color:red}. aa {Color:blue}--&L T;/style> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa</textarea>
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One.

Web standards are not allowed to duplicate ID, such as div id= "AA" is not allowed to repeat 2 times, and the class is defined by classes, theoretically can be infinitely repeated, so that the definition of multiple references can be used.

Two.
Priority issues for attributes
The priority of ID is higher than class, see the example above

Three.
Convenient JS and other client-side script, if you want to script an object in the page, then you can define an ID, otherwise can only be used to traverse the page element plus specify a specific attribute to find it, this is a relatively waste of time resources, far less than a simple ID.
11. How to center text vertically
<textarea id="runcode45999"><! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 strict//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" > < Meta http-equiv= "Content-type" content= "text/html; charset=gb2312 "/> <style type=" Text/css "> <!--div {height:30px; line-height:30px; BORDER:1PX Solid Red}-</style> Web standards FAQs</textarea>
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Set a container with the same height as it would be.
12. How to align text and input baskets
<textarea id="runcode23973"><! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 strict//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" > < Meta http-equiv= "Content-type" content= "text/html; charset=gb2312 "/> <style type=" Text/css "> <!--input {width:200px; height:30px; border:1px solid red; --</style> <input type= "text"/>aaaaaaaaaaaaaaaaaa</textarea>
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If you encounter this problem, set the vertical-align:middle of the text box.

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