So i want to put letter limitations into text boxs, not like it will pop up
an error but not be able to write letters and only numbers, as
the column type in db is demical.

Sounds like you're looking for is_numeric() or perhaps even is_int()

that would help me pop up an error but not to stop user from putting a letter into text box.

<HTML>
<HEAD>
<TITLE>Letting Only Numbers Pass to a Form Field</TITLE>
<SCRIPT LANGUAGE="JavaScript">
function checkIt(evt) {
    evt = (evt) ? evt : window.event
    var charCode = (evt.which) ? evt.which : evt.keyCode
    if (charCode > 31 && (charCode < 48 || charCode > 57)) {
        status = "This field accepts numbers only."
        return false
    }
    status = ""
    return true
}
</SCRIPT>
</HEAD>

<BODY>
<H1>Letting Only Numbers Pass to a Form Field</H1>
<HR>
<FORM onSubmit="return false">
Enter any positive integer: <INPUT TYPE="text" NAME="numeric" 
    onKeyPress="return checkIt(event)">
</FORM>
</BODY>
</HTML>

just got this first hit off google.
saved me typing it hope it helped :)

<HTML>
<HEAD>
<TITLE>Letting Only Numbers Pass to a Form Field</TITLE>
<SCRIPT LANGUAGE="JavaScript">
function checkIt(evt) {
    evt = (evt) ? evt : window.event
    var charCode = (evt.which) ? evt.which : evt.keyCode
    if (charCode > 31 && (charCode < 48 || charCode > 57)) {
        status = "This field accepts numbers only."
        return false
    }
    status = ""
    return true
}
</SCRIPT>
</HEAD>

<BODY>
<H1>Letting Only Numbers Pass to a Form Field</H1>
<HR>
<FORM onSubmit="return false">
Enter any positive integer: <INPUT TYPE="text" NAME="numeric" 
    onKeyPress="return checkIt(event)">
</FORM>
</BODY>
</HTML>

thats better. soz

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