The message of "Page not found" on the homepage

[Dave]

So even when you upload the original forum.php and index.php file, the same problem is happening?
Definitely a bad plugin/hook or .htaccess file.

[SWSUSA]

Originally Posted by Dave

So even when you upload the original forum.php and index.php file, the same problem is happening?

Yes. Да.

Originally Posted by Dave

Definitely a bad plugin/hook or .htaccess file.

I assume that it because of settings of the web server or because of one of the established spendthrifts.

Я предполагаю, что это из-за настроек веб-сервера или из-за одного из установленных модов.

--------------- Added [DATE]1449667976[/DATE] at [TIME]1449667976[/TIME] ---------------

I solved a problem. It because of a code in the .htaccess file.
With such code the site ceased to open:

Решил проблему. Это из-за кода в файле .htaccess.
С таким кодом сайт перестал открываться:

# Block User-agent Libwww-perl
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} libwww-perl.* 
RewriteRule .* – [F,L]

<IfModule mod_rewrite.c>
	RewriteEngine On

	# If you are having problems or are using VirtualDocumentRoot, uncomment this line and set it to your vBulletin directory.
	# RewriteBase /

	# If you are having problems with the rewrite from content/ to content.php, uncomment this line to turn MultiViews off.
	# Options -MultiViews

	RewriteCond %{REQUEST_URI} !(admincp/|dbseocp/|modcp/|cron|mobiquo|forumrunner|api\.php|reviewpost/|classifieds/|photopost/)
	RewriteRule ^((archive/)?(.*\.php(/.*)?))$ dbseo.php [L,QSA]

	RewriteCond %{REQUEST_FILENAME} !-f
	RewriteCond %{REQUEST_FILENAME} !-d
	RewriteCond %{REQUEST_FILENAME} !/(admincp|dbseocp|modcp|clientscript|cpstyles|images|reviewpost|classifieds|photopost)/
	RewriteRule ^(.+)$ dbseo.php [L,QSA]
</IfModule>

# proc/self/environ? no way!
RewriteCond %{QUERY_STRING} proc/self/environ [OR]
# Block out any script trying to set a mosConfig value through the URL
RewriteCond %{QUERY_STRING} mosConfig_[a-zA-Z_]{1,21}(=|%3D) [OR]
# Block out any script trying to base64_encode crap to send via URL
RewriteCond %{QUERY_STRING} base64_encode.*(.*) [OR]
# Block out any script that includes a <script> tag in URL
RewriteCond %{QUERY_STRING} (<|%3C).*script.*(>|%3E) [NC,OR]
# Block out any script trying to set a PHP GLOBALS variable via URL
RewriteCond %{QUERY_STRING} GLOBALS(=|[|%[0-9A-Z]{0,2}) [OR]
# Block out any script trying to modify a _REQUEST variable via URL
RewriteCond %{QUERY_STRING} _REQUEST(=|[|%[0-9A-Z]{0,2})

With such code the site opens:
С таким кодом сайт открывается:

# Block User-agent Libwww-perl
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} libwww-perl.* 
RewriteRule .* – [F,L]

# proc/self/environ? no way!
RewriteCond %{QUERY_STRING} proc/self/environ [OR]
# Block out any script trying to set a mosConfig value through the URL
RewriteCond %{QUERY_STRING} mosConfig_[a-zA-Z_]{1,21}(=|%3D) [OR]
# Block out any script trying to base64_encode crap to send via URL
RewriteCond %{QUERY_STRING} base64_encode.*(.*) [OR]
# Block out any script that includes a <script> tag in URL
RewriteCond %{QUERY_STRING} (<|%3C).*script.*(>|%3E) [NC,OR]
# Block out any script trying to set a PHP GLOBALS variable via URL
RewriteCond %{QUERY_STRING} GLOBALS(=|[|%[0-9A-Z]{0,2}) [OR]
# Block out any script trying to modify a _REQUEST variable via URL
RewriteCond %{QUERY_STRING} _REQUEST(=|[|%[0-9A-Z]{0,2})

<IfModule mod_rewrite.c>
	RewriteEngine On

	# If you are having problems or are using VirtualDocumentRoot, uncomment this line and set it to your vBulletin directory.
	# RewriteBase /

	# If you are having problems with the rewrite from content/ to content.php, uncomment this line to turn MultiViews off.
	# Options -MultiViews

	RewriteCond %{REQUEST_URI} !(admincp/|dbseocp/|modcp/|cron|mobiquo|forumrunner|api\.php|reviewpost/|classifieds/|photopost/)
	RewriteRule ^((archive/)?(.*\.php(/.*)?))$ dbseo.php [L,QSA]

	RewriteCond %{REQUEST_FILENAME} !-f
	RewriteCond %{REQUEST_FILENAME} !-d
	RewriteCond %{REQUEST_FILENAME} !/(admincp|dbseocp|modcp|clientscript|cpstyles|images|reviewpost|classifieds|photopost)/
	RewriteRule ^(.+)$ dbseo.php [L,QSA]
</IfModule>

The part of this code is necessary for fashion [DBTech] of DragonByte SEO v2 (vB4). Though itself fashions at me it is switched off.
Часть этого кода нужна для мода [DBTech] DragonByte SEO v2 (vB4). Хотя сам мод у меня выключен.

The part of this code optimizes a forum, increasing the speed of loading of pages.
Часть этого кода оптимизирует форум, увеличивая скорость загрузки страниц.

[Dragonsys]

glad you got it figured out, but did you not tell us that you didn't make any changes, it just suddenly started happening? If you had told us about the changes made to .htaccess we could have figured it out sooner

[SWSUSA]

Originally Posted by Dragonsys

glad you got it figured out, but did you not tell us that you didn't make any changes, it just suddenly started happening? If you had told us about the changes made to .htaccess we could have figured it out sooner

I did changes in the .htaccess file 5 months ago.
Изменения в файле .htaccess я делал 5 месяцев назад.

I think that the company the owner of a hosting made some changes on a hosting though they also won't confess in it. I saw on a hosting there were new functions and new folders, just that day when my site ceased to open. And this code in the .htaccess file ceased to work normally.
Я думаю, что компания владелец хостинга внесла какие-то изменения на хостинге, хотя они и не сознаются в этом. Я видел на хостинге появились новые функции и новые папки, как раз в тот день, когда мой сайт перестал открываться. И этот код в файле .htaccess перестал нормально работать.

[Dragonsys]

Originally Posted by SWSUSA

I did changes in the .htaccess file 5 months ago.
Изменения в файле .htaccess я делал 5 месяцев назад.

I think that the company the owner of a hosting made some changes on a hosting though they also won't confess in it. I saw on a hosting there were new functions and new folders, just that day when my site ceased to open. And this code in the .htaccess file ceased to work normally.
Я думаю, что компания владелец хостинга внесла какие-то изменения на хостинге, хотя они и не сознаются в этом. Я видел на хостинге появились новые функции и новые папки, как раз в тот день, когда мой сайт перестал открываться. И этот код в файле .htaccess перестал нормально работать.

ahh ok, I would open a ticket to your host and ask them what changes they made recently then. They might have upgraded PHP or Apache, but it would be handy for you to know what they are doing