One of the most tedious aspects of establishing a uniquely themed Open Journal or Open Conference Systems site is in getting the CSS to work as you would like. While there are varying schools of thought regarding best practice for implementing cross browser compatibility, my chosen methodology is to write compliant XHTML 1.0 Transitional markup, followed by valid CSS 2 that should do the job, followed by the moderate contamination of conditional comments to include style sheets for Internet Explorer 6 and 7 where compliance isn't achieved. OJS and OCS provide many ways of getting raw markup into the document but, to the best of my knowledge, no way of injecting into the head field. Anyway, here's the solution (simple, I know, but might save someone looking for a longer period). Simple replace the closing head tag with the following inside templates/common/header.tpl
<!--[if lte IE 6]> <link href="{$baseUrl}/styles/ie6.css" rel="stylesheet" type="text/css"> <![endif]-->
<!--[if IE 7]> <link href="{$baseUrl}/styles/ie7.css" rel="stylesheet" type="text/css"> <![endif]-->
You can then edit ie6.css and ie7.css which are conditionally included. Don't forget to add !important tags to any overrides which don't give a higher level of specificity than set in earlier sheets.