CSS problem - an element only works if its has no parent (using jquery)

问题

i have this code:

CSS:

.taglist 
{
    float:left;
    margin-left:30px;
}
.taglist ul 
{
    overflow:auto;
    list-style-type:none;
    border:1px solid #999;
    background:#ccc;
    padding:20px;
    min-height:150px;
    max-height:150px;
    width:100px;
}

.taglist li
{
    display:block;
    border:1px solid #999;
    background:#fff;
    width:80px;
    padding:5px 10px;
    margin-bottom:5px;
}
.tag_selected {
    background:#ffc;
}

HTML:

<div class="taglist">
    <ul id="list1">
        <li id="1">1</li>
    </ul>
</div>

Now I'm using jQuery for this one.. so when an item on the list is selected, it should change its class to tag_selected.

Problem is, it only works if i remove the ".taglist " before the ul and li css, and i don't want to do it because i want the style only to be on the "taglist" div..

i'v tried every combination like ".taglist tag_selected", ".taglist ul li tg_selected", etc. but nothing works !!

what can I do?

btw, trying this line:

<li class="tag_selected" id="1">1</li>

gave the same result, no change what so ever..

Thanks in advance!

回答1:

Your problem seems to be CSS selector specificity.

The rules .taglist ul and .taglist li are more specific than .tag_selected and therefore your class is assigned but the background is overridden by .taglist li.

This should work

.taglist li.tag_selected {
    background:#ffc;
}

The specificity order (weakest to strongest) tag, class, ID. The easiest way to remember to calculated it is treat the sum of each as a digit, with tag as the 1s, class as the 10s, and ID as the 100s.

• li - 1
• .taglist - 10
• .taglist li - 11
• li#myId - 101
• div.taglist li.tag_selected - 22

See http://htmldog.com/guides/cssadvanced/specificity/ for help or Google "css specificity".

来源：https://stackoverflow.com/questions/4330423/css-problem-an-element-only-works-if-its-has-no-parent-using-jquery