I've had feedback from someone who is blind which is that parts of one of my ecommerce websites are not accessible to visually impared people. In particular, the Paypal button at the point of submitting the order which this person says she just cannot find. I'll provide the code I've used to make up the Paypal button and wondered if someone might be able to tell me what I need to do to make it accessible to visually impared people. I put in alt and title tags but that hasn't helped.

I've also been told making websites accessible to visually impared people is a legal requirement. I have tried to find this information on Google but am unable to confirm. Is anyone able to confirm this?

HTML Code:
<form action="cart.php?stage=complete" method="post" style="margin: 0px; padding: 0px;">
<fieldset style="border: none;">
	<input type="hidden" name="paymentType" value='sale' />
	<input type="hidden" name="L_NAME[]" value="" />
	<input type="hidden" name="L_DESC[]" value="" />
	<input type="hidden" name="L_AMT[]" value="" />
	<input type="hidden" name="L_QTY[]" value="" />
	<input type="hidden" name="CUSTOM" value="" />
	<input type="hidden" name="count" value="" />
	<input type="hidden" name="subtotal" value="" />
	<input type="hidden" name="currencyCodeType" value="GBP" />
	<input type="hidden" name="INVNUM" value="" />
	<input type="hidden" name="SHIPPING" value="" />
	<input type="hidden" name="SHIPPING_METHOD" value="" />
	<input type="hidden" name="PERSONNAME" value="" />
	<input type="hidden" name="SHIPTOSTREET" value="" />
	<input type="hidden" name="SHIPTOCITY" value="" />
	<input type="hidden" name="SHIPTOZIP" value="" />';
	<input type="hidden" name="SHIPTOCOUNTRYCODE" value="" />
	<input type="image" name="submit" src="https://www.paypal.com/en_US/i/btn/btn_xpressCheckout.gif" alt="Paypal Button" title="Paypal Button" style="width: 60%; border: none;" />
Thanks in advance