Q:

how to remove css from the text box?

The question might sound dumb... but I have a code that is applying a css on a text box. now I want it to be set as default again on another condition.
Or to be precise I want to sent my textbox to its default style.
Searching on the internet and stackoverflow I have fount these answers - 
Default textbox border-style and width
Any help?
EDIT :
    if (condition)
        {
            txtLastName.CssClass="ControlBackground_Yellow"; 
        }
    else
        {               
            txtLastName.CssClass="ControlBackground_White"; 
        }

css is --
ControlBackground_Yellow    
{
    background-color:#FFFF00;
}

ControlBackground_White     
{
    background-color:#FFFFFF;
}

PS:sorry not allowed to use jQuery

A:

You can use jQuery to remove css class from your control based on certain condition:
 var $arrow = jQuery('<div class="arrow"></div>');

 $arrow.removeClass();

You can again add class:
 $arrow.addClass('className');

