Try this this should work:
trStudData = strStudData + string.Format("<img src='images/{0}.jpg' width='150' height='41' align='absmiddle' /> {1} {2} {3} <span class='style3' style='background-color:#0066FF;color:White;'> {4} </span> ", readStud.Rows[i][4].ToString().Trim(), readStud.Rows[i][0].ToString(), readStud.Rows[i][1].ToString(), readStud.Rows[i][2].ToString(), readStud.Rows[i][3].ToString());
Sreekanth