Edit in JSFiddle

<h3>Speedmonitor</h3>
<form id="addUrlForm">
    <label for="url">Url</label>
    <input id="url" type="text" />
    <input id="submit" type="submit" />
</form>
<table id="urlTable">
    <tr>
        <td>Url</td>
        <td>Load Speed (ms)</td>
        <td></td>
    </tr>
</table>

// In this array, we'll keep track of the urls and their last fetch time.
var urls = [
    {url: "www.google.com", loadSpeed: 50},
    {url: "angularjs.org", loadSpeed: 75},
    {url: "www.dwmkerr.com", loadSpeed: 120}
];
    
// This function will update the url table, making sure we've got the urls..
function updateUrlTable() {
    
    // Get the table.
    var table = document.getElementById("urlTable");
    
    // Clear old table rows, but not the heading...
    var rows = table.rows.length - 1;
    for(var i=0; i<rows; i++) {
        table.deleteRow(1);
    }
    
    // Now add a row for each entry.
    for(i=0; i<urls.length; i++) {
        var row = table.insertRow(table.rows.length);
        var cell1 = row.insertCell(0);
        var cell2 = row.insertCell(1);
        var cell3 = row.insertCell(2);
        cell1.innerHTML = urls[i].url;
        cell2.innerHTML = urls[i].loadSpeed + " ms";
        cell3.innerHTML = '<a href="javascript:void(0)" onclick="removeUrl(' + i + ');">Delete</a">';
    }    
}

// This function deletes a row. It's added on the window as we're in an onload...
function removeUrl(index) {
    // Remove the url by index.
    urls.splice(index, 1);
    
    // Update the table.
    updateUrlTable();
}

// This function adds an url.
function addUrl(url) {
    
    // Add a new url entry.
    urls.push({
        url: url,
        loadSpeed: Math.random()*75+50
    });
    
    // Update the table.
    updateUrlTable();
}

// When the form is submitted, add the url.
var form = document.getElementById("addUrlForm");
form.onsubmit = function() {
    addUrl(document.getElementById("url").value);
    return false;
};

// First time through, update the table.
updateUrlTable();