title: How to change the table row background color while the conditions fails?
body: <p>I am merging three coloumns and showing the merged values in the 4th column, am appliying some rules for merge operation. In some case that rules will bring up null value and display it in any row in the 4th column, i want to highlight the null row alone in RED color.</p>
  
  <p>Like listed below.</p>
  
  <p>Value1</p>
  
  <p>Value2</p>
  
  <p>NULL(Red color)</p>
  
  <p>Value 4</p>
  
  <p>please help me on this, Am working in wicket framework.</p>