firefox absolute positioning overlap

I am having trouble rendering this correctly in firefox. It renders nicely in chrome and in safari.

<div style="" id="login_inline">
    <form accept-charset="utf-8" action="/users/login" method="post" id="UserLoginForm">
    <div style="display:none;">
        <input type="hidden" value="POST" name="_method">
    </div>
    <input type="text" id="UserDummyEmail" tabindex="1" value="Email" name="data[User][dummyEmail]" style="display: block;">
    <input type="text" id="UserDummyPassword" tabindex="2" value="Password" name="data[User][dummyPassword]" style="display: block;">
    <input type="text" id="UserEmail" maxlength="255" tabindex="3" name="data[User][email]">
    <input type="password" id="UserPassword" tabindex="4" name="data[User][password]">
    <div class="submit">
        <input type="submit" value="Login">
    </div>
    </form>
</div>

CSS:

#login_inline {
position:absolute;
right:10px;
top:30px;
width:420px;
}

.submit {
display:inline;
position:absolute;
left:360px;
}

#UserPassword {
position:absolute;
left: 185px;
}

#UserDummyPassword {
position:absolute;
left:185px;
z-index:1;
color:gray;
}

#UserDummyEmail {
position:absolute;
left:10px;
z-index:1;
color:gray;
}

#UserEmail {
position:absolute;
left:10px;
}

Firefox rendering:

Chrome rendering:

EDIT: Live example (Correct rendering)

By positioning absolute you become dependent on correct width of the input elements. This is difficult to do cross-browser because browsers tend to use custom or native elements that don't style consistently. You're better off with an inline-block or floated layout that handles inconsistent width.

If you really have to do it that way there are some hacks using css3 box-sizing property and/or manually tuning properties like line-height and font size and padding to get all browsers to agree on input sizing but that's harder than it sounds.

This question has some info on box-sizing and using percentage/auto width to get consistency: input with display:block is not a block, why not?

EDIT: Based on your comment above you may need to set up some div wrappers to set the size/position of both the hidden and visible elements and then use percentage widths and box-sizing as explained.

<div class="input_wrapper" style="width:100px;position:relative">
    <input style="width:100%;box-sizing:border-box;position:absolute">
    <div class="fake_input" style="width:100%;position:absolute">
</div>

The key to it all is that box-sizing:border-box is less susceptible to browser differences in padding and border calculations on form inputs.