blazmedia on "[Plugin: Contact Form 7] Alertbox ajax error/confirmation messages"

I was running into the same thing. I just found a way that works for me. I hop this can help you as well.

In the style sheet go to:

div.wpcf7-mail-sent-ok {
	border: 2px solid #398f14;
}

I then changed that line add this code to match the theme I am working on:

div.wpcf7-mail-sent-ok {
        display:none;
        background: #fff;
        padding: 10px;
        border: 5px solid #F0EFEF;
        float: left;
        font-size: 1.2em;
        position: fixed;
        top: 50%; left: 30%;
        z-index: 99999;
        box-shadow: 0px 0px 5px #999; /* CSS3 */
        -moz-box-shadow: 0px 0px 5px #999; /* Firefox */
        -webkit-box-shadow: 0px 0px 5px #999; /* Safari, Chrome */
         border-radius:5px 5px 5px 5px;
        -moz-border-radius: 5px; /* Firefox */
        -webkit-border-radius: 5px; /* Safari, Chrome */
}

You can do this for each alert that you will have. You can change the text in the Contact Form 7 interface.