比如这个框：<input type="text" name="yzm" size="4" maxlength="4" onBlur="regInput(this)" />



检验代码

<script language="javascript">

function regInput(targ)

{

if(!/^-?\d*\.?\d{0,2}$/.test(targ.value)){targ.value='';targ.focus()}

}

</script>