.htaccess & Server Side Includes

Please help. I am a 100% newbie to this and usually research and copy code no training etc.

Doing a site redesign (~150 pages) was directed to server side includes and fell in love - could not get them to work. Hosting company (NTT Verio - shared) said I needed to use .shtml to get it to work -

Did not want to spend my life renaming all my pages and loosing the several thousand links established - found out about .htaccess files and things were great. Then found out our shopping cart (ShopSite) did not work - error 403 "You are not authorized to view this page" .

Verio support sent me the following
Unable to access ShopSite store ________________________________________________________________

We have researched the issue and found that you a unsupported .htaccess modification file in the site root.

If you rename .htaccess to .htaccess.old, the store works fine.

The following line is the cause:

Options Indexes FollowSymLinks Includes

********

I thought that line was a must have.

My current .htaccess file reads

**********
Options Indexes FollowSymLinks Includes
AddType application/x-httpd-cgi .cgi
AddType text/x-server-parsed-html .html
RewriteEngine on
RewriteRule ^qvis_index\.htm$ qvis_index5.shtml
RewriteRule ^process%20management%20and%20mapping%20with%20QViS\.htm$ QViS2.shtml
RewriteRule ^contact_us\.htm$ contact_us.shtml
*************

What are my options?

Thank You!!!
Ralph Ising
847-546-9841

I removed this line from my .htaccess file as per Verio support

Options Indexes FollowSymLinks Includes

My page re-directs to pages that use #Include .. Server side includes seem to be working just fine.
The ones that call cgi files (forms etc) seem to work
and my shopping cart from ShopSite seems to work.

So, my question is, why have I been told that this line is critical?
What does it do (in simple english)
What problems can arise from not having it?
How is this going to bite me in the behind later?

Thanks!
Ralph

I have no clue why they said oyu need it. My .htaccess file doesn't ahve it and it works just fine, and always has