WEBPlotter

The WEBPlotter is a Microsoft ActiveX or Netscape plugin module intended for viewing the HP-GL/2, HP-GL and HP-RTL files on WEB pages. 

WEBPlotter ActiveX Control V2.01 for Win32

System Requirements: Windows 95/98/Me or Windows NT/2000/XP. 

The ActiveX version of WEBPlotter was developped as a replacement of the WEBPlotter plugin under Microsoft Internet Explorer. ActiveX is a Microsoft technology, whereas plugin is a Netscape technology. So it is clear that support of the plugin technology is not ideal under MSIE and even it seems that under latest versions of MSIE (MSIE 5.5 SP2 and MSIE 6.0) this support is abandoned. 

The ActiveX version of WEBPlotter can theoretically run under any ActiveX container (e.g. MS Word, MS Excell etc.), however it was tested only under MSIE. 

WEBPlotter Plug-In V2.01 for Win32 

System Requirements: Windows 95/98/Me or Windows NT. 

The Netscape Navigator 2.0 or higher or MS Internet Explorer 4.0 or higher (32-bit). 

Warning: The latest versions of Microsoft Internet Explorer (MSIE 5.5 SP2 and MSIE 6.0) do not support correctly Netscape plugins. So you must use the ActiveX version of WEBPlotter for these versions of MSIE. It is generally better to use ActiveX version also under earlier versions of MSIE. ActiveX is a Microsoft technology, whereas plugin is a Netscape technology. 

The WEBPlotter plugin is a 32-bit application so it runs only under 32-bit browsers (it does not run under MS Internet Explorer for Win 3.x and WinNT 3.51 because this is 16-bit browser). 

The WEBPlotter plugin supports these MIME types and extensions: 

MIME type	Extensions
application/vnd.hp-HPGL	.plt;.hpg;.hgl;.hpgl
vector/x-hpgl	.plt;.hpg;.hgl;.hpgl
vector/x-hpgl2	.plt;.hpg;.hgl;.hp2;.hpgl2

You should have at least one from the listed MIME types registered on your WEB server. I recommend to use the application/vnd.hp-HPGL MIME type, because it is officially registered by the IANA organization. 
From view of WEBPlotter module it is not important which of listed MIME types you will use, because WEBPlotter works with HP-GL/2 as well as with HP-GL files independently of MIME type name.