Cross-Site Scripting or Cascading Style Sheets?
Cross-Site scripting is handled on the server side, and the web server (Apache) sends HTML pages to the browser. If these pages are broken then they won't display. Save these pages as raw HTML files and upload them to http://validator.w3.org/
to check them. If they validate, then they should render on any standards-complient browser; if not then they may not render on any.
The only way to test if code will render on IE is to try and render it on IE. There are many bugs in IE's handling of HTML that Microsoft refuse to fix on the grounds that companies exist who rely on this broken behaviour.
Style-sheets contain rules for rendering other data, like HTML. So you can't render them. Rendering is handled entirely by the web browser; Apache just serves CSS files to the browser.
IE is a very common web browser with many
known bugs in rendering style-sheets. For the most common instance, it treats the “width” attribute as the element width including borders, margin and padding, rather than the standard which excludes borders, margin and padding.
First of all, check that your CSS code is valid. Go to http://jigsaw.w3.org/css-validator/
and upload your CSS style-sheet. This will tell you if there are any problems with it. If your stylesheet has problems then you'll be lucky to find any browser that will render it.