Found the following HTML validation problems:
feasible_overlap.html:59:25: Warning: entity "&nbsp" doesn't end in ';'
feasible_overlap.html:60:1: Warning: entity "&nbsp" doesn't end in ';'
feasible_overlap.html:60:27: Warning: entity "&nbsp" doesn't end in ';'
feasible_overlap.html:66:83: Warning: unescaped & or unknown entity "&#8804"
feasible_overlap.html:67:44: Warning: entity "&nbsp" doesn't end in ';'
wrangle_ellipse.html:98:17: Warning: unescaped & or unknown entity "&#8712"
wrangle_ellipse.html:98:71: Warning: unescaped & or unknown entity "&#8804"
wrangle_ellipse.html:99:17: Warning: unescaped & or unknown entity "&#8712"
wrangle_ellipse.html:99:84: Warning: unescaped & or unknown entity "&#8804"
wrangle_ellipse.html:100:17: Warning: unescaped & or unknown entity "&#8712"
wrangle_ellipse.html:100:84: Warning: unescaped & or unknown entity "&#8804"
wrangle_ellipse.html:101:17: Warning: unescaped & or unknown entity "&#8712"
wrangle_ellipse.html:101:97: Warning: unescaped & or unknown entity "&#8804"
wrangle_ellipse.html:102:17: Warning: unescaped & or unknown entity "&#8712"
wrangle_ellipse.html:102:80: Warning: unescaped & or unknown entity "&#8804"
wrangle_ellipse.html:103:17: Warning: unescaped & or unknown entity "&#8712"
wrangle_ellipse.html:103:81: Warning: unescaped & or unknown entity "&#8804"
wrangle_ellipse.html:104:17: Warning: unescaped & or unknown entity "&#8712"
wrangle_ellipse.html:104:68: Warning: unescaped & or unknown entity "&#8804"
wrangle_ellipse.html:105:17: Warning: unescaped & or unknown entity "&#8712"
wrangle_ellipse.html:105:69: Warning: unescaped & or unknown entity "&#8804"
wrangle_ellipse.html:106:1: Warning: inserting implicit <p>
wrangle_ellipse.html:98:1: Warning: <center> element removed from HTML5
wrangle_ellipse.html:99:1: Warning: <center> element removed from HTML5
wrangle_ellipse.html:100:1: Warning: <center> element removed from HTML5
wrangle_ellipse.html:101:1: Warning: <center> element removed from HTML5
wrangle_ellipse.html:102:1: Warning: <center> element removed from HTML5
wrangle_ellipse.html:103:1: Warning: <center> element removed from HTML5
wrangle_ellipse.html:104:1: Warning: <center> element removed from HTML5
wrangle_ellipse.html:105:1: Warning: <center> element removed from HTML5