Pseudo-element after not showing? [duplicate]

问题

This question already has an answer here:

Why do the :before and :after pseudo-elements require a 'content' property? 4 answers

I want to add a help logo at the end of some form fields which opens a tooltip.

Everything is working, but the .helptip icon (http://img1.wsimg.com/shared/img/1/small-help-icon.gif) is coming on the left(merged) with the text. I actually want in on the right of span text, so I did .help-tip:after. But then nothing shows up at all.

Can you spot what's wrong?

<div class="advancedSearchFormSelectField fclear">
<span id="view_format_mis" class="advancedSearchFormlabel help-tip"> Include Columns in Result Set </span>

<select class="advancedSearchFormSelectBox" id="filters_include_columns" multiple="multiple" name="filters[include_columns][]">

<option value="x">X</option>
<option value="y">Y</option>
<option value="z">Z</option>
</select>
</div>

<div class="advancedSearchFormSelectField fclear">
<span id="view_format_mis" class="advancedSearchFormlabel"> Sort Column </span>
<!--No help tip here -->    
<select class="advancedSearchFormSelectBox" id="filters_sort_columns" multiple="multiple" name="filters[sort_columns]">

<option value="a">A</option>
<option value="b">B</option>
<option value="c">C</option>
</select>
</div>

.help-tip {
/* Merged text at the moment. .help-tip:after not working */ 
    cursor: pointer;
    width: 10px;
    height: 10px;
    background-repeat: no-repeat;
    background-image: url("/assets/small-help-icon.gif");
}

.advancedSearchFormSelectField{
    width:300px;
    margin: 5px;
    height: 60px;
    float:left;
}

回答1:

You don't seem to be using a pseudo-element at the moment. Try this setting .help-tip to .help-tip::after and giving is content: "" and display: inline-block:

.help-tip::after {
    content: "";
    display: inline-block;
    cursor: pointer;
    width: 10px;
    height: 10px;
    background-repeat: no-repeat;
    background-image: url("/assets/small-help-icon.gif");
}

来源：https://stackoverflow.com/questions/15783361/pseudo-element-after-not-showing

标签

css

css3

pseudo-element