.assistive-text h3 in 1px square?

Hello. I have some h3 headers with text "Main Menu", "Submenu" in a square clip.. Look at this css (it's default theme css): /* Assistive text */ .assistive-text { position: absolute !important; clip: rect(1px 1px 1px 1px); /* IE6, IE7 */ clip: rect(1px, 1px, 1px, 1px); } SO this text is actually hidden What is this? Can I remove this assistive-text bock from the page template or it will affect some problems? Don't wanna any hidden h3 on every page This block is located before menu and submenu, maybe it's some WP default stuff BUT this definitely isn't the best way to hide these headers