is it necessary to have website validation 100%

i've recently been test the validation of my pages in dreamweaver and they are ok apart from the ones where i have paypal buttons and radio buttons, does this mean that for some people browsing they wouldnt' see my buttons because of the errors?

i'm doing a whole new site and need radio buttons and paypal buttons but if this code does bring up errors then i need to look again and see how to do it so it does validate

here is the code if anyone is interested to see why it doesn't validate?

Code:
<script language="javascript">
function GetSelectedItem() {

chosen = ""
len = document.myform.os0.length

for (i = 0; i <len; i++) {
if (document.myform.os0[i].checked) {
chosen = document.myform.os0[i].value
}
}

if (chosen == "3/4 x 4") {
 document.myform.amount.value = 3.99;
 document.myform.item_name.value = "3/4 x 4 Arrow Wraps X 12 + 1 Free";
    }
if (chosen == "1 x 4") {
 document.myform.amount.value = 3.99;
 document.myform.item_name.value = "1 x 4 Arrow Wrap X 12 + 1 Free";
    }        
if (chosen == "1 x 7") {
 document.myform.amount.value = 4.49;
 document.myform.item_name.value = "1 x 7 Arrow Wrap X 12 + 1 Free";
    }
if (chosen == "1.25 x 7") {
 document.myform.amount.value = 4.49;
 document.myform.item_name.value = "1.25 x 7 Arrow Wrap X 12 + 1 Free";
    }        


}


</script>
			<form target="paypal" method="post" name="myform" action="https://www.paypal.com/cgi-bin/webscr">
				<input type="hidden" name="item_name" value="5/8 x 4">
				<input type="hidden" name="amount" value="3.99">
				<input type="hidden" name="on0" value="Colour">
				<p align="left">
				<input name="os0" type="radio" value="5/8 x 4"><font size="2">5/8&quot; x 4&quot;&nbsp;&nbsp;&nbsp;&nbsp; 
				£3.99 
				</font> <br>
				<input name="os0" type="radio" value="3/4 x 4"><font size="2">3/4&quot; x 4&quot;&nbsp;&nbsp;&nbsp;&nbsp; 
				£3.99 
				</font> <br>
				<input name="os0" type="radio" value="1 x 4"><font size="2">1&quot; x 4&quot;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
				£3.99 
				</font> <br>
				<input name="os0" type="radio" value="1 x 7"><font size="2">1&quot; x 7&quot;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
				£4.49 </font><br>
				<input name="os0" type="radio" value="1.25 x 7"><font size="2">1.25&quot; 
				x 7&quot;&nbsp;&nbsp; £4.49 </font><br>
				<br>
				&nbsp;<select name="os0">
				<option value="Red">Red</option>
				<option value="Orange">Orange</option>
				<option value="Yellow">Yellow</option>
				<option value="Green">Green</option>
				<option value="Blue">Blue</option>
				<option value="Pink">Pink</option>
				<option value="Violet">Violet</option>
				<option value="Silver">Silver</option>
				<option value="White">White</option>
				</select><br>
				<img alt="" border="0" src="Page8files/pixel.gif" width="1" height="1">
				<input type="hidden" name="add" value="1">
				<input type="hidden" name="cmd" value="_cart">
				<input type="hidden" name="business" value="Payments@quickstandarchery.co.uk">
				<input type="hidden" name="page_style" value="PayPal">
				<input type="hidden" name="no_shipping" value="2">
				<input type="hidden" name="return" value="http://www.quickstandarchery.co.uk/page8.html">
				<input type="hidden" name="currency_code" value="GBP">
				<input type="hidden" name="lc" value="UK">
				<input type="hidden" name="bn" value="PP-ShopCartBF">
				<input type="image" src="Page8files/x-click-but22.gif" border="0" name="submit" onClick="GetSelectedItem()" alt="Please choose color and size" align="left" hspace="2" width="87" height="23"></p>
			</form>