How to remove spaces between cells in a html table

Question

I try to remove white space between Table1Header and Table2Header. I tried border:0px, padding:0px and border-spacing:0px; styles. Firefox and Opera tell me that my border-spacing style is overrided by the user agent style (which is 2px). How can I force browser to use my styleshits?

http://jsfiddle.net/cdjDR/2/

<table class="tableGroup">
    <tbody>
        <tr>
            <td>
                <table>
                    <tbody>
                        <tr class="tableHeader">
                            <td><span class="tableHeader"><label>Table1Header</label></span>

                            </td>
                        </tr>
                        <tr class=" tableData">
                            <td>
                                <div class="ui-datatable">
                                    <div>
                                        <table>
                                            <thead>
                                                <tr>
                                                    <th>
                                                        <div><span><span class="ui-header-text">Table1Col1</span></span>
                                                        </div>
                                                    </th>
                                                </tr>
                                            </thead>
                                            <tbody>
                                                <tr>
                                                    <td><span>2</span>

                                                    </td>
                                                </tr>
                                            </tbody>
                                        </table>
                                    </div>
                                </div>
                            </td>
                        </tr>
                    </tbody>
                </table>
            </td>
            <td>
                <table>
                    <tbody>
                        <tr class="tableHeader">
                            <td><span class="tableHeader"><label>Table2Header</label></span>

                            </td>
                        </tr>
                        <tr class="tableData">
                            <td>
                                <div class="ui-datatable">
                                    <div>
                                        <table>
                                            <thead>
                                                <tr>
                                                    <th>
                                                        <div><span><span class="ui-header-text" >Table2Col1</span></span>
                                                        </div>
                                                    </th>
                                                </tr>
                                            </thead>
                                            <tbody>
                                                <tr>
                                                    <td><span>12345</span>

                                                    </td>
                                                </tr>
                                            </tbody>
                                        </table>
                                    </div>
                                </div>
                            </td>
                        </tr>
                    </tbody>
                </table>
            </td>
        </tr>
    </tbody>
</table>

span.tableHeader > label {
    display: inline-block;
    float:left;
    line-height:30px;
    padding-left:10px;
    color: #202020;
    font-size: 13px;
}
tr.tableHeader {
    background-color: #EEEEEE;
}
table.tableGroup, table.tableGroup > tr > td > table {
    border-spacing: 0px;
}
table.tableGroup div.ui-datatable th > div > span >span.ui-header-text {
    color: #808080;
    font-size: 11px;
}
table.tableGroup td, table.tableGroup th {
    padding: 0px;
    border: 0px;
}

Answer 1

You can simply use border-collapse: collapse; or even border-spacing: 0; is fine

table { /* Will apply to all tables */
    border-spacing: 0;
    /* OR border-collapse: collapse; */
}

Demo

You can easily override the useragent stylesheet with a simple element selector.

---

If you want to normalize the styles, you should use CSS Reset

---

Coming to your selector which is seems dirty to me, as yo are targeting the table with class .tableGroup and the table nested under that

table.tableGroup, table.tableGroup > tr > td > table {
    border-spacing: 0px;
}

So you better use

table.tableGroup, 
table.tableGroup table {
   border-spacing: 0;
}