I'll try
but you need to rethink the 'id's you have chosen
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>National Vehicle Movements - Booking Form</title>
<style type="text/css">
<!--
body { background-color: #1d255f; margin: 0; padding: 0; }
#apDiv1 {
position:absolute;
width:487px;
height:706px;
z-index:auto;
left: 50%;
top: 433px;
font-family: Arial, Helvetica, sans-serif;
font-size: 10px;
font-weight: bold;
text-align: center;
textarea-align: center;
background-position: center;
margin-left: -244px;
}
-->
</style>
<script type='text/javascript'>
function validatethis() {
if(!document.getelementById('Is Vehicle Roadworthy with Full M.O.T.').value='Yes') { Alert('The vehicle must be roadworthy with full M.O.T'); return false;}
if(!document.getelementById('checkbox').checked='checked') { Alert('You must agree to the Terms and Conditions'); return false;}
return true;}</script>
</head>
<body>
<div align="left">
<div id="apDiv1">
<form id="form1" name="form1" method="post" action="sendform.php" onsubmit='validatethis();'>
<table width="400" border="0" align="center">
<tr>
<td width="193" align="right">Company:</td>
<td width="197" ><input type="text" name="company" id="Company" /></td>
</tr>
<tr>
<td align="right">Name:</td>
<td ><input type="text" name="name" id="Name" /></td>
</tr>
<tr>
<td align="right">Phone Number:</td>
<td ><input type="text" name="phonenum" id="Phone Number" /></td>
</tr>
<tr>
<td align="right">Email Address:</td>
<td ><input type="text" name="email" id="Email" /></td>
</tr>
<tr>
<td align="right">Vehicle Make and Model:</td>
<td ><input type="text" name="vmam" id="Vehicle Make and Model" /></td>
</tr>
<tr>
<td align="right">Vehicle Reg./Ref. No.:</td>
<td><input type="text" name="vreg" id="Vehicle Reg." /></td>
</tr>
<tr>
<td align="right">Collection Address including Postcode:</td>
<td><textarea name="colladd" rows="4" id="Collection Address"></textarea></td>
</tr>
<tr>
<td align="right">Collection Contact Name:</td>
<td><input type="text" name="collconname" id="Collection Contact Name" /></td>
</tr>
<tr>
<td align="right">Collection Contact Number:</td>
<td><input type="text" name="collconnum" id="Collection Contact Number" /></td>
</tr>
<tr>
<td align="right">Delivery Address including Postcode:</td>
<td ><textarea name="deladd" rows="4" id="Delivery Address"></textarea></td>
</tr>
<tr>
<td align="right">Delivery Contact Name:</td>
<td><input type="text" name="delconname" id="Delivery Contact Name" /></td>
</tr>
<tr>
<td align="right">Delivery Contact Number:</td>
<td><input type="text" name="delconnum" id="Delivery Contact Number" /></td>
</tr>
<tr>
<td align="right">Collection Date/Time:</td>
<td><input type="text" name="collectiondt" id="Collection Date/Time" /></td>
</tr>
<tr>
<td colspan="2" valign="top" align='center'><em>(if possible please give a time window eg. '7th - 9th August' and we will arrange collection for you)</em></td>
</tr>
<tr>
<td align="right">Delivery Date/Time:</td>
<td><input type="text" name="deliverydt" id="Delivery Date/Time" /></td>
</tr>
<tr>
<td colspan="2" valign="top" align='center'><em>(if possible please give a time window eg. '7th - 9th August' and we will arrange delivery for you)</em></td>
</tr>
<tr>
<td align="right">Is Vehicle Taxed:</td>
<td><select name="Taxed" id="Is Vehicle Taxed">
<option>Yes</option>
<option selected="selected">No</option>
</select></td>
</tr>
<tr>
<td align="right">Is Vehicle roadworthy with full M.O.T.:</td>
<td><select name="mot" id="Is Vehicle Roadworthy with Full M.O.T.">
<option>Yes</option>
<option selected="selected">No</option>
</select></td>
</tr>
<tr>
<td align="right">Billing Address:</td>
<td><textarea name="billadd" rows="3" id="Billing Address"></textarea></td>
</tr>
<tr>
<td colspan="2" valign="top" align='center'><em>(if same as collection or delivery address please enter 'collection' or 'delivery')</em></td>
</tr>
<tr>
<td align="right">Your Ref./Order No. (if any):</td>
<td><input type="text" name="custordnum" id="Customer Ref./Order No." /></td>
</tr>
<tr>
<td align="right">Any additional comments:</td>
<td><textarea name="addcom" rows="3" id="Any additional comments"></textarea></td>
</tr>
<tr>
<td colspan="2" align="center" valign="middle">
<p>
<input type="checkbox" name="checkbox" id="checkbox" />
<label for='checkbox'>I agree with the <u><a href="Terms.html">Terms and Conditions</a></u></label></p>
<p> </p></td>
</tr>
<tr>
<td colspan="2" align='center'><input type="submit" name="button" id="button" value="Submit order" />
<input type="reset" name="button2" id="button2" value="Reset form" /></td>
</tr>
</table>
</form>
</div>
</div>
<div align="center"><img src="images/Booking_03.jpg" width="680" height="1352" border="0" usemap="#Map" />
<map name="Map" id="Map">
<area shape="rect" coords="36,155,158,173" href="index.html" alt="Home" />
<area shape="rect" coords="29,174,151,189" href="Prices.html" alt="Prices" />
<area shape="rect" coords="475,191,578,206" href="mailto:info@n-v-m.co.uk" alt="Email us" />
</map>
</div>
</body>
</html>
0px is an invalid style that may throw browsers into quirks mode, 0px=0em=0%=0pt=0inch=0cm=$0=0lb0oz=0Kg= 0
other notes
fixed size fonts etc dont work, 10px is .09inch high on this monitor
current best practice for layout is ems and %, relative sizes that adjust to user basefont settings
if you set <table width='60%'><tr><td width='50%'></td><td width='50%'></td></tr></table> it will autoadjust
if you set fonts as 100% for regular text 125% for emphasis 85% for subscripts then the viewer will always be able to see the text in its designed layout, even if its a hires monitor with a basefont of 24px, or aunt Harriet who is visually impaired (blind as a bat) and has her basefont set to 72px
not going to mention that tables are a lousy layout tool, lot of code little content,
small steps towards css
