Use a normal link to submit a form

You are using images to submit.. so you can simply use an type="image" input "button":

<input type="image" src="yourimage.png" name="yourinputname" value="yourinputvalue" />

Just styling an input type="submit" like this worked for me:

.link-button { 
     background: none;
     border: none;
     color: #1a0dab;
     text-decoration: underline;
     cursor: pointer; 
}

<input type="submit" class="link-button" />

Tested in Chrome, IE 7-9, Firefox

You can't really do this without some form of scripting to the best of my knowledge.

<form id="my_form">
<!-- Your Form -->    
<a href="javascript:{}" onclick="document.getElementById('my_form').submit(); return false;">submit</a>
</form>

Example from Here.

Two ways. Either create a button and style it so it looks like a link with css, or create a link and use onclick="this.closest('form').submit();return false;".