MOdule Carousel Banner

How can i center the title when the screen resize?

The width of the page is 436 px.
<a href="/desarrollo/component/banners/click/11" title="">
<img src="www.myweb.es/desarrollo/images/Banners/BackgroundWebB.jpg" alt="Foro Mariano" width="262" height="400">
<br><div class="carousel-galeria-title">myweb</div>
</a>

this is the css of title that i´ve got:

.carousel-galeria-title:hover{
color: #8b4d31;

}

.carousel-galeria-title {
margin-top: -100px;

font-size: 15px;
color: #000040;
background-color: red;
border-color: #e1e7ed;
opacity: 0.8;
background-color: #e1e7ed;
margin-bottom: 20px;
with:320px;
font-weight: bolder;
max-width:300px;
}

It doesn´t work. when the size of the the screen is 1064.8px. the width os the carousel-galeria-title tend to be the width of banneritem-inner and sometimes this width is not the same as img.