Center Data in [one-half]

Hi,

i am using the [one-half] function to seperate my page in 2 parts.

<p style="text-align: justify;">[one-half-first]<a href="https://www.salvenmoser.org/wordpress/der-drachenflieger" target="_top" onmouseover="document.sub_but.src='https://www.salvenmoser.org/wordpress/Images/Drachenflieger.jpg'" onmouseout="document.sub_but.src='https://www.salvenmoser.org/wordpress/Images/Drachenflieger_sw.jpg'">
 <img src='https://www.salvenmoser.org/wordpress/Images/Drachenflieger_sw.jpg' style=border:0px solid #cc3300;" alt="Move your mouse over me" name="sub_but">
 </a>[/one-half-first]
[one-half]<a href="https://www.salvenmoser.org/wordpress/der-glaser" target="_top" onmouseover="document.sub_but1.src='https://www.salvenmoser.org/wordpress/Images/Glaser.jpg'" onmouseout="document.sub_but1.src='https://www.salvenmoser.org/wordpress/Images/Glaser_sw.jpg'">
 <img src='https://www.salvenmoser.org/wordpress/Images/Glaser_sw.jpg' style=border:0px solid #cc3300;" alt="Move your mouse over me" name="sub_but1">
 </a>[/one-half]</p>

The Pictures are correct on their half of the page, but i am not able to Center them in this half. How does this work?

Thanks your help!