Product Version = NetBeans IDE 8.1 (Build 201510222201)
Operating System = Windows 7 version 6.1 running on amd64
Java; VM; Vendor = 1.8.0_91
Runtime = Java HotSpot(TM) 64-Bit Server VM 25.91-b14

Reproducibility: Happens every time

STEPS:
  * Run Maven Web application
 Value of XML element <param-value>false</param-value> 
in
    <init-param>
      <param-name>mappedfile</param-name>
      <param-value>false</param-value>
    </init-param>

was changed to true when NetBeans starts TomCat server. This settings alow to generate jsp files bigger than 65Kb. Without this parameter set to true not able to generate this big jsp pages in application.
If I start TomCat manualy from command line the web.xm file was not changed.

ACTUAL:
  I solve this problem by set attribute of web.xml file to read only but it is not nice solution. I saw this problem in your BugZilla system like Bug 227177 but I mean this problem is still in version 8.1. Can you solve this problem in NetBeans?

EXPECTED:
  message pops u