How to change header in table with custom CSS

Hello,
I want to change de layout of the header of my table with the customer CSS.
I tried this example example html css
Below a part of the css

.zui-table thead th {
background-color: #DDEFEF;
border: solid 1px #DDEEEE;
color: #336B6B;
padding: 10px;
text-align: left;
text-shadow: 1px 1px 1px #fff;
}

Below part of the table.

<table class=”zui-table zui-table-horizontal zui-table-highlight”>
<thead>
<tr>
<th>Name</th>
<th>Position</th>
<th>Height</th>
<th>Born</th>
<th>Salary</th>
</tr>

The header of my table is not changed. It had still the Nirvana theme style.

When i change the table like below it works.

<table class=”zui-table zui-table-horizontal zui-table-highlight”>
<thead>
<tr>
<th style=”background-color: #DDEFEF;
border: solid 1px #DDEEEE;
color: #336B6B;
padding: 10px;
text-align: left;
text-shadow: 1px 1px 1px #fff;>Name</th>

Why it doesn’t work with Customer CSS ?

Thanks in advance.

Kr
Ingo

Website: www.bergezelkes.be/new_blog