Texbox Accepts only numbers and decimal point

use this js it will work

function isn(evt)
{
var charCode = (evt.which) ? evt.which : event.keyCode
var str=evt.value;
if ((str.indexOf('.')>=0) && (event.keyCode==46)) return false;

          if (charCode != 46 && charCode > 31
            && (charCode < 48 || charCode > 57))
             return false;

          return true;

}

in your js i have added only this two line

var str=evt.value;
if ((str.indexOf'.')>=0) && (event.keyCode==46)) return false;

What you need to do is to check the whole contents of the textbox and scan for the decimal. if decimal is found then return false for it. also make sure it is done in onkeypress event and not any other event.

here is some sample code. populate the value variable with your controls value and you are good to go.

//Get the text of text box in a variable called value here
            for(var s=0; s<value.length; ++s)
            {
                if(value.charCodeAt(s) == '.'.charCodeAt(0))
                {
                   return false;
                }
            }