What did you find?

Replaced file with original just to get text and put my own edited one back

W3C CSS Validator results for http://calstock.org.uk/elf.php (CSS level 3)
Sorry! We found the following errors (7)
URI : http://calstock.org.uk/rsc/build/b2evo_base.bmin.css?v=6.7.7-stable-2016-10-01
1 a.rollover_sprite:hover span.icon Value Error : visibility Too many values or values are not recognized : visible\000000 /
1 Unknown dimension 0\0
1 Parse Error ){a.rollover_sprite:hover span.icon{visibility:visible}}
1 a.roundbutton, a.roundbutton_text, span.roundbutton attempt to find a semi-colon before the property name. add it
1 a.roundbutton, a.roundbutton_text, span.roundbutton Property progid doesn't exist : DXImageTransform
1 a.roundbutton, a.roundbutton_text, span.roundbutton Parse Error DXImageTransform.Microsoft.gradient(startColorstr='#f5f5f5', endColorstr='#bababa')}
1 unrecognized media \000000screen \0screen{#styled_contentblock span[class*=status] span,.evo_contentblock span[class*=status] span{top:-15px;left:-2px}}

@amoun @fplanque I see all the reports are IE 8 and 9 specific rules (hacks?).

I guess there is not too much to do than to live with them until our IE support is raised to a decent (ehem!, I meant standard ;) ) version of that browser.