How to Fix Page not Found Errror In WordPress

Hello all,

Some days ago my one of WordPress site get hacked and for the reason I needed to reintall and rebuild the site again.
But No I facing a lot of Page Not Found Error in my6 WP sit.
and I can not fix the problem.

There are about 1678 page not found within 12 days.

So, My question is Can you please help me about that How can I fix the problem of Page not found Error in WordPress.
I would be happy if you kindly give a helpful replay.

What is causing these errors? Are the pages in question pages that used to be part of your site, but which you have since removed, or are they pages which were added by the hacker and have now been deleted?

This error has been occurred when you have changed your Wordpress permalink structure. Don’t worry about it, it is very easy. follow below steps:
Look for .htaccess file in your FTP program, open its CHMOD settings & change 644 to 666.
Now click Wordpress site’s admin section, click Settings then Permalinks.
Edit the link structure to whatever you want & save.
Finally, for security measure, go back to your FTP space and change your .htaccess file from 666 back to 644.

Some are my site’s link and some are Hacked link. I mean I Did not have any database backup, so I have lost all posts, tag everything.
Now I have to fix them. I saw that some links are unknown which was the previous theme’s link.
Now can you tell me boss , ow can i fix them?

[FONT=Verdana]OK. Error messages for pages added by the hacker, you can ignore. Eventually, the search engines will realise that these pages no longer exist and stop looking for them. Anybody linking to one of these pages is not somebody you really want to have linking to you, so you don’t need to worry about them.

For the pages which used to exist, ideally, you should set up a 301 redirect for each of the old pages to the nearest equivalent new page. If that’s not possible, then your best course of action may be to set up a custom 404 page, explaining that the page requested no longer exists and offering quick links to the main areas of your site, so that people can easily find what they’re looking for.

Submitting a new sitemap may also help to get your new structure correctly indexed by the search engines.[/FONT]

Dear Sir,

Thank you so much for your early helpful replay. I already done 301 Redirect task.
Now my question is if I redirect my some page to 301 then will it harm my site in search engine or affect by Google?

[FONT=Verdana]

No. The redirect tells search engines that the information which used to be at [noparse]yourdomain.com/pathto/oldpage[/noparse] can now be found at [noparse]yourdomain.com/pathto/newpage[/noparse], and the 301 code tells them that this change is permanent. So the search engines will update their records and stop looking for the old pages which no longer exist. So it will in no way harm your site, and should help it.[/FONT]

Thank you so much Sir,
I thought that It will harm my site and for the reason I was unwilling to redirect my pages to 301.
I think you know that there is a Plugin for WordPress to redirect them.
I am happy to know from you that I can use the Plugin i my WordPress site easily Now Right?
Thanks again for your helpful suggestion Dear Sir.

I am facing same porblem in my site <snip>. I have 81 page not found errors but it is made in codeigniter. I exported the list of url which are not found by search engines. Can you help me how to make 301 redirects in codeigniter.