Introduction to the difference between background and _background in CSS properties

The CSS style sheet has the following statement:

. imminbox {width:39px; height:29px;padding-right:3px; cursor:pointer; position:absolute; right:1px; bottom:0px; z-index:20; overflow:visible; Background:url (.. /images/im_minbar.png) No-repeat; _background:url (.. /images/im_minbar.gif) No-repeat; Top:auto;}

Do not know how the _background attribute should be understood

*html. Imbox{position:absolute;bottom:auto;top:expression (eval (document.documentelement.scrolltop+ document.documentelement.clientheight-this.offsetheight-(parseint (this.currentstyle.margintop,10) | | 0)-(parseint (this.currentstyle.marginbottom,10) | | 0))-35);}

CSS has such a sentence, "*html" what meaning, how to understand it?

1,_background is the Hank attribute of IE6, with "_" in front of the style attribute only IE6 can recognize; the style runs from the yearning and runs until it cannot be executed.

Like what

style{color: #000000;                  /* FF,OP Support */color: #0000FF \9;       /* All browser IE browser (ie6+) support, but IE8 does not recognize "*" and "_" CSS hack; so we can write hack */[color: #000000; color: #00FF00;      /* SF,CH Support */*color: #FFFF00;                 /* IE7 Support */_color: #FF0000;                 /* IE6 support */}

2, about *html. Imbox
Also belongs to the IE 6 Hank. Set up to solve specific problems with IE 6.

*html is the hack notation for IE6, equivalent to the above _background:url (...). The "_ Property" used in the.

This property is usually followed by a normal property, such as. class{background:blue; _background:red;}, meaning that the IE6 background color is blue and the IE6 background color is red. The wording of the change to *html is:. class {Background:blue;} *html. class{background:red}, which is an effect.

This is due to different versions of IE problem, _background this attribute is only for IE6 effect! Because IE6 is not supported for PNG transparent properties! So when the user browser is IE6, it will automatically use the _background style! You don't see the background picture in GIF format.