div#mainPreloaded div {
  background-repeat: no-repeat;
}

div#bAUCZA {background-image: url(./images/buttonAboutUsCZActive.gif)}
div#bAUENA {background-image: url(./images/buttonAboutUsENActive.gif)}

div#bCCZA {background-image: url(./images/buttonCompaniesCZActive.gif)}
div#bCENA {background-image: url(./images/buttonCompaniesENActive.gif)}

div#bLCZA {background-image: url(./images/buttonLanguageCZActive.gif)}
div#bLENA {background-image: url(./images/buttonLanguageENActive.gif)}

div#bSCZA {background-image: url(./images/buttonStudentsCZActive.gif)}
div#bSENA {background-image: url(./images/buttonStudentsENActive.gif)}