function ShowTable()
{
var show = document.getElementById("table");
var tableHead = "<Table Border='1' width='100%'>";
var tableBottom = "</table>";
var tableBody="";
var j;
j = document.frm1.txtValue.value;
for(var i = 0; i < j; i++){
tableBody = tableBody + "<tr><td>1</td><td>2</td><td>3</td><td>4</td><td>5</td></tr>";
}
show.innerHTML = tableHead + tableBody + tableBottom ;
}

<form name="frm1">
Number of Rows: >input type="text" name="txtValue">
</form>
<input type=button name="shwTable" value="Show Table" onClick="javascript:ShowTable();">
<div id="table"></div>