Seems unlikely that CSS could cause that problem.
Shouldn't make a difference but you could try:
{{=A('hello', _href=URL(c='default', f='index'))}}To figure out if the CSS is to blame, if you are on Chrome or Safari, right-click on the text and select "Inspect Element" (or use Firebug on Firefox). Finally, does that link work OK in a fresh app like "welcome"?
