Although it is trivial bug, but I hope it will be fix at next release.
OS: Microsoft Windows Server 2008 R2
DB: Microsoft SQL Server 2012
mojoPotal: 2.4.0.2(Also confirmed on 2.4.0.4 Demo site ad Nov 4th, 2014)
.NET: 4.5
Steps.
1. Create Items that Radio Button and CheckBox on Survey new page.
2. Turned on to [Answer Required] and required settings for both items.
3. Run Survey, and then just click [Finish] button.
3. You will see the answer required message, but they are different styles. It seems class="txterror" property is missing for CheckBox.
Radio Button:
<span id="ctl00_mainContent_ctl01_vala5c892ca540644f69cda0c3505335762" class="txterror" style="visibility:hidden;">Answer required</span>
CheckBox:
<span id="ctl00_mainContent_ctl04_valb20eb8de456c403995e6bffd9d1341c1" style="visibility:hidden;">Answer required</span>