.zahlavi {width: 100%;background-color: dodgerblue;height: 50px;text-align: center;font-size: 40px}

.clanek {box-sizing: border-box;width: 100%;height: 609px;margin: 20px 0;padding: 15px;background-color: dodgerblue;}

@media screen and (min-width: 900px) {.clanek {width: 79%;float: left;}}

.postranni-panel {box-sizing: border-box;width: 100%;height: 300px;margin: 10px 0;padding: 10px;background-color: dodgerblue;}

@media screen and (min-width: 900px) {.postranni-panel {width: 19%;float: right}}

.panel_1 {text-align: center;background-color:dodgerblue}

.panel_2 {text-align: center;background-color: dodgerblue}