CSS-tables: selector tr:hover is not working as expected?

Question

Why in this CSS code the background color in (#customers tr:hover) selector is not working for the first tr element which contains the th element and have green background.

#customers {
  font-family: Arial, Helvetica, sans-serif;
  border-collapse: collapse;
  width: 100%;
}

#customers td,
#customers th {
  border: 1px solid #ddd;
  padding: 8px;
}

#customers tr:nth-child(even) {
  background-color: #f2f2f2;
}

#customers tr:hover {
  background-color: #ddd;
}

#customers th {
  padding-top: 12px;
  padding-bottom: 12px;
  text-align: left;
  background-color: #04aa6d;
  color: white;
}

<h1>A Fancy Table</h1>

<table id="customers">
  <tr>
    <th>Company</th>
    <th>Contact</th>
    <th>Country</th>
  </tr>
  <tr>
    <td>Alfreds Futterkiste</td>
    <td>Maria Anders</td>
    <td>Germany</td>
  </tr>
  <tr>
    <td>Berglunds snabbköp</td>
    <td>Christina Berglund</td>
    <td>Sweden</td>
  </tr>
  <tr>
    <td>Centro comercial Moctezuma</td>
    <td>Francisco Chang</td>
    <td>Mexico</td>
  </tr>
  <tr>
    <td>Ernst Handel</td>
    <td>Roland Mendel</td>
    <td>Austria</td>
  </tr>
  <tr>
    <td>Island Trading</td>
    <td>Helen Bennett</td>
    <td>UK</td>
  </tr>
  <tr>
    <td>Königlich Essen</td>
    <td>Philip Cramer</td>
    <td>Germany</td>
  </tr>
  <tr>
    <td>Laughing Bacchus Winecellars</td>
    <td>Yoshi Tannamuri</td>
    <td>Canada</td>
  </tr>
  <tr>
    <td>Magazzini Alimentari Riuniti</td>
    <td>Giovanni Rovelli</td>
    <td>Italy</td>
  </tr>
  <tr>
    <td>North/South</td>
    <td>Simon Crowther</td>
    <td>UK</td>
  </tr>
  <tr>
    <td>Paris spécialités</td>
    <td>Marie Bertrand</td>
    <td>France</td>
  </tr>
</table>

Here is the link: https://www.w3schools.com/css/tryit.asp?filename=trycss_table_fancy

When i read this code from w3schools i was expecting that all tr elements will have a background color of #ddd on hover, but it didn't work for the first one.

is there some kind of restriction on the first tr !?

I am quite new to HTML/CSS so it might be obvious, but it would be nice with some help. Thanks.

Answer 1

You did not declare a background color for td, only th. Therefore, when hover changes the background color of tr, the th background color does not change. (th is on top of tr, so the tr background color is not visible.) To change the background color of all ths in a tr when any th in the row is hovered, just include an additional selector: #customers tr:hover th

#customers {
  font-family: Arial, Helvetica, sans-serif;
  border-collapse: collapse;
  width: 100%;
}

#customers td,
#customers th {
  border: 1px solid #ddd;
  padding: 8px;
}

#customers tr:nth-child(even) {
  background-color: #f2f2f2;
}

#customers tr:hover,
#customers tr:hover th {
  background-color: #ddd;
}

#customers th {
  padding-top: 12px;
  padding-bottom: 12px;
  text-align: left;
  background-color: #04aa6d;
  color: white;
}

<h1>A Fancy Table</h1>

<table id="customers">
  <tr>
    <th>Company</th>
    <th>Contact</th>
    <th>Country</th>
  </tr>
  <tr>
    <td>Alfreds Futterkiste</td>
    <td>Maria Anders</td>
    <td>Germany</td>
  </tr>
  <tr>
    <td>Berglunds snabbköp</td>
    <td>Christina Berglund</td>
    <td>Sweden</td>
  </tr>
  <tr>
    <td>Centro comercial Moctezuma</td>
    <td>Francisco Chang</td>
    <td>Mexico</td>
  </tr>
  <tr>
    <td>Ernst Handel</td>
    <td>Roland Mendel</td>
    <td>Austria</td>
  </tr>
  <tr>
    <td>Island Trading</td>
    <td>Helen Bennett</td>
    <td>UK</td>
  </tr>
  <tr>
    <td>Königlich Essen</td>
    <td>Philip Cramer</td>
    <td>Germany</td>
  </tr>
  <tr>
    <td>Laughing Bacchus Winecellars</td>
    <td>Yoshi Tannamuri</td>
    <td>Canada</td>
  </tr>
  <tr>
    <td>Magazzini Alimentari Riuniti</td>
    <td>Giovanni Rovelli</td>
    <td>Italy</td>
  </tr>
  <tr>
    <td>North/South</td>
    <td>Simon Crowther</td>
    <td>UK</td>
  </tr>
  <tr>
    <td>Paris spécialités</td>
    <td>Marie Bertrand</td>
    <td>France</td>
  </tr>
</table>

---

Hmm, I explained the issue and provided a working solution but got downvoted... Here's more examples to prove my point.

In this example, background-color is declared only for tr:hover

tr:hover {
  background-color: red;
}

<table>
  <tr>
    <th>Company</th>
    <th>Contact</th>
    <th>Country</th>
  </tr>
  <tr>
    <td>Alfreds Futterkiste</td>
    <td>Maria Anders</td>
    <td>Germany</td>
  </tr>
  <tr>
    <td>Berglunds snabbköp</td>
    <td>Christina Berglund</td>
    <td>Sweden</td>
  </tr>
  <tr>
    <td>Centro comercial Moctezuma</td>
    <td>Francisco Chang</td>
    <td>Mexico</td>
  </tr>
</table>

In this example, tr background-color is overruled by the background-color of th and td

th {
  background-color: #04aa6d;
}

td {
  background-color: #f2f2f2;
}

tr, tr:hover {
  background-color: red;
}

<table>
  <tr>
    <th>Company</th>
    <th>Contact</th>
    <th>Country</th>
  </tr>
  <tr>
    <td>Alfreds Futterkiste</td>
    <td>Maria Anders</td>
    <td>Germany</td>
  </tr>
  <tr>
    <td>Berglunds snabbköp</td>
    <td>Christina Berglund</td>
    <td>Sweden</td>
  </tr>
  <tr>
    <td>Centro comercial Moctezuma</td>
    <td>Francisco Chang</td>
    <td>Mexico</td>
  </tr>
</table>

This example uses higher specificity with tr:hover th and is able to change the background-color on hover.

th {
  background-color: #04aa6d;
}

td {
  background-color: #f2f2f2;
}

tr:hover th {
  background-color: orange;
}

tr:hover td {
  background-color: yellow;
}

tr, tr:hover {
  background-color: red;
}

<table>
  <tr>
    <th>Company</th>
    <th>Contact</th>
    <th>Country</th>
  </tr>
  <tr>
    <td>Alfreds Futterkiste</td>
    <td>Maria Anders</td>
    <td>Germany</td>
  </tr>
  <tr>
    <td>Berglunds snabbköp</td>
    <td>Christina Berglund</td>
    <td>Sweden</td>
  </tr>
  <tr>
    <td>Centro comercial Moctezuma</td>
    <td>Francisco Chang</td>
    <td>Mexico</td>
  </tr>
</table>