[TYPO3-english] Removing default Block Styles

[Emiliano Kamppeter]

Hello,

I have figured out how to add my custom Blockstyles, but I just can't 
find how to remove the following, standard block styles:
align-left, align-right, centered, alignjsutify, box with yellow 
background, box with grey background.

I would really appreciate if someone could tell me how this could be 
achieved.

Thanks so much,

Emiliano