+1  A: 

The difference between the unstyled and styled buttons is that the unstyled buttons don't have an attribute of class="button".

You should be able to log into WP, click plugins, click edit on the Subscribe2 plugin and find where the input type=submit buttons are and add a class="button" to them.

<input type="submit" class="button" value="Subscribe" name="subscribe"/>
<input type="submit" class="button" value="Unsubscribe" name="unsubscribe"/>

Edit: In your css file, you will want to create a class called button:

.button {
  background-color: #e0ffff;
  color: #ffffff;
}

You'll need to change/add these values to something that suits you. You can find out more about css at w3schools. You will probably want to look at background, text, font, and box model.

Alright, I got it this time!

Change line 949 in style.css to this:

#submitbox #submit, .button {

Change line 960 in style.css to this:

#submitbox #submit:hover, .button:hover {
Andy Gaskell
Button definitions appear tens of times in the plugin's PHP code. Most of them include either class="button-primary" or class="button-secondary". There was button definition without class definition, I added class="button" to it but it didn't change the appearance.
Roee Adler
Can you show me a page on your blog that has correctly styled buttons? I was going off of the button styling that the iNove theme had.
Andy Gaskell
I've put 3 buttons at the About page, of classes "button", "button-primary" and "button-secondary". All look the same. What's wrong?
Roee Adler
I'm sorry, I misunderstood. I thought there were buttons on the iNove theme that you liked and weren't showing up on your plugin. I will edit my answer.
Andy Gaskell
I updated my question, please take a look, thanks.
Roee Adler
We should be really close now - updated answer.
Andy Gaskell
You're the king!
Roee Adler