Is there a way to specify that you want a text in all Capital letters within a CSS Style Sheet?

There sure is!

Simply set the property 'text-transform' to the value 'uppercase', like this:
.allCapital
{
text-transform: uppercase;
}

and use the class "allCapital" on the elements you want.

Some other interesting values:
text-transform: capitalize /* capitalises every first letter of each word */
text-transform: lowercase /* all lowercase */

Jakob