<p>  
<label for="userName">不允许输入空格</label>  
<input type="text" name="userName" id="userName" onkeyup="this.value=this.value.replace(/[^\w]/g,'');"  />   
</p>  
<p>  
<label for="number">只允许输入数字</label>  
<input type="text" name="number" id="number" onkeyup="this.value=this.value.replace(/[^\d]/g,'');"  />   
</p>