<html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Check that UnderBar is visible when stretched</title> <style type="text/css"> html { background-color: white; font-size: 50px } mi { color: white; } mo { color: black; } </style> </head> <body> <math xmlns="http://www.w3.org/1998/Math/MathML"> <munder> <mi>long</mi> <mo>̲</mo> </munder> </math> </body> </html>