Cols, colgroups and css ":hover" pseudoclass

Here's a pure CSS method using no JavaScript.

I used ::before and ::after pseudo-elements to do the row and column highlighting. z-index keeps the highlighting below the <td>s in case you need to handle click events. position: absolute allows them to leave the confines of the <td>. overflow: hidden on the <table> hides the highlight overflow.

It wasn't necessary, but I also made it select just the row or column when you're in the headers. The .row and .col classes take care of this. If you wish the simplify, you can remove them.

This works in all modern browsers (and degrades gracefully on older browsers by doing nothing).

Demo: http://jsfiddle.net/ThinkingStiff/rUhCa/

Output:

CSS:

table {
    border-spacing: 0;
    border-collapse: collapse;
    overflow: hidden;
    z-index: 1;
}

td, th, .row, .col {
    cursor: pointer;
    padding: 10px;
    position: relative;
}

td:hover::before,
.row:hover::before { 
    background-color: #ffa;
    content: '\00a0';  
    height: 100%;
    left: -5000px;
    position: absolute;  
    top: 0;
    width: 10000px;   
    z-index: -1;        
}

td:hover::after,
.col:hover::after { 
    background-color: #ffa;
    content: '\00a0';  
    height: 10000px;    
    left: 0;
    position: absolute;  
    top: -5000px;
    width: 100%;
    z-index: -1;        
}

HTML:

<table>
    <tr>
        <th></th>
        <th class="col">50kg</th>
        <th class="col">55kg</th>
        <th class="col">60kg</th>
        <th class="col">65kg</th>
        <th class="col">70kg</th>
    </tr>
    <tr>
        <th class="row">160cm</th>
        <td>20</td><td>21</td><td>23</td><td>25</td><td>27</td>
    </tr>
    <tr>
        <th class="row">165cm</th>
        <td>18</td><td>20</td><td>22</td><td>24</td><td>26</td>
    </tr>
    <tr>
        <th class="row">170cm</th>
        <td>17</td><td>19</td><td>21</td><td>23</td><td>25</td>
    </tr>
    <tr>
        <th class="row">175cm</th>
        <td>16</td><td>18</td><td>20</td><td>22</td><td>24</td>
    </tr>
</table>

There is a very decent jQuery plugin I've come across located here which does a very good job of this kind of thing with loads of examples. Preferentially I'd use that.