[Plugin: WP Calendar] Strange column style

this is not a WP Calendar Problem. Check your theme’s css (default.css) where you find the following style definition:

table { border-collapse: collapse; border-spacing: 0; border: 1px solid #CCC; }
th, td { padding: 5px; border: 1px solid #CCC; border-width: 1px; }
th, thead th { font-weight: 700; color: #333; background: #DDD; }
td, tbody td { background: #F0F0F0; }

make sure you overwrite these rules for the calendar like this:

.fc table { border: none; } /* Disabled Borders of whole tables */
.fc-header td, .fc-header th { border: none; background-color: white; } /*Disabled borders of cells*/

Cheers

i don’t understand your questing? it is all about the stylesheet. i think this is the default style and my calendar looks excatly alike. you should check your stylesheet and not apply styles to tags (e.g. table, td) but to classes and/or ideas instead or you should cascade your styles using other selectors.