/* 内联样式 */
<input type="text" style="color: red; border: 1px solid blue;">
/* 外部样式表 */
.inputstyle {
color: red;
border: 1px solid blue;
}<form> <label for="username">用户名:</label> <input type="text" id="username" name="username" placeholder="请输入用户名" required> <br> <label for="password">密码:</label> <input type="password" id="password" name="password" maxlength="16" required> <br> <label for="email">邮箱:</label> <input type="email" id="email" name="email" placeholder="请输入邮箱" required> <br> <input type="submit" value="提交"> </form>