div tag alignment from code-behind.

Hi all..

I have a webPage.aspx as -









Now,
in aspx.cs code on button click - I have

btn_click
{
if(txt_stud_ID.Lenght > 0 && txt_FName.Lenght > 0 && txt_LName.Lenght > 0)
{
// Insert
}
else
{
div_errormsg.Innertext = "Enter proper values";
}
}
--------
Now, I want that - If Stud_ID is not there, then the "div_errormsg" must be below the Stud_ID text box.
If the FName is not there , then the "div_errormsg" must be below the FName text box.
---
How to align this div from code-behind user the textbox controls ??