1- edit the file includes/languages/english/shopping_cart.php
and customize to your own taste the section below

define('TEXT_CART_EMPTY', '<strong>You have emptied your Shopping Cart.</strong><br /><br />
If you did not find the right article or if something made you change your mind, <br />please let us know by filling in the form below :<br /><br /><form action="http://<yourdomain.com>/cgi-bin/cgiemail/wwwdev/mymailtemplate/mailtempl2.txt" METHOD="POST" NAME="emptycart">
<input type="checkbox" name="testing" value="yes">&nbsp;I was just browsing and checking the shop
<br>
<input type="checkbox" name="product" value="yes">&nbsp;Products are not what I want after all
<br>
<input type="checkbox" name="price" value="yes">&nbsp;Prices are too high
<br>
<input type="checkbox" name="payment" value="yes">&nbsp;Payment modes are not suitable
<br>
<input type="checkbox" name="shipping" value="yes">&nbsp;Shipping costs are too high
<br><br>Other reasons / additional comments :<br>
<textarea name="emptycartmessage" rows="10" style="background: #AFD3E0; width:400px;" value="" id="emptycartmessage"></textarea><br>
<br>
You can provide your e-mail address if you expect a response to your feedback :<br>
<input name="email" style="width:165px; height:14px; background: #AFD3E0;"><br><br>
<input name="Submit" type="submit" value="SEND" style="border: 2px outset #d7b9c9; background: #AFD3E0;" title="">

<INPUT TYPE="hidden" NAME="success" VALUE="http://viaterra.net/store/index.php?main_page=contact_us&action=success">
</form>');

2- create and customize the mail template file mailtempl2.txt
which you save in <yourdomain.com>/cgi-bin/cgiemail/wwwdev/mymailtemplate/ (path may depend on your hosting service)

To: youremail@yourdomain.com
Subject: empty cart feedback

was just browsing and checking the shop = [testing]
Products are not what I want after all = [product]
Prices are too high = [price]
Payment modes are not suitable = [payment]
Shipping costs are too high = [shipping]
additional comments = [emptycartmessage]
email address = [email]
IP = [$REMOTE_ADDR]
Agent = [$HTTP_USER_AGENT]

3- test your form : add an item to your cart, remove it, fill in the form and check your email

Any questions, let me know.
Denis

Useful resources :
http://web.mit.edu/wwwdev/cgiemail/user.html