To forward your website to secure URL you need to put the following redirect rule in .htaccess under public_html.

RewriteEngine on
Options +FollowSymLinks
RewriteCond %{SERVER_PORT} !^443$
RewriteRule ^.*$ https://%{SERVER_NAME}%{REQUEST_URI} [L,R]

This code will redirect http://yourdomain.com to https://yourdomain.com.

To use this rule mod_rewrite module should be installed on the server by default.

To redirect domain.com to www.domain.com you need to add following mod_rewrite rule in .htaccess file which is inside public_html.

RewriteEngine on
RewriteCond %{HTTP_HOST} ^domain\.com
RewriteRule ^(.*)$ http://www.domain.com/$1 [R=permanent,L]

To use this mod_rewrite you will need this modile to be enabled on the server.

Make sure that you replace domain.com with your actual domain name in the above code.

1. Web Site Accessibility

Validating your html code helps to pinpoint areas of potential blockage that could prevent search engine spiders or visitors from accessing your website. When you run your site through a code validator it may produce many errors that need to be corrected so your pages will render well. ie include text with your “alt” tags for every tag.

2. Search engine friendly pages

Clean and simple code enables search engines to spider your pages more quickly and completely.

3. Faster Loading

If your web page contains html errors it will take a longer time for the search engines to spider it, therefore
slowing the loading time. If your page doesn’t load in under 10 seconds your visitors will click away to your competitors’ sites.

4. Less load on servers

Clean and simple code won’t tax your server as much as a site which has complicated code or contain many nested tables. Cascading style sheets (CSS) will greatly reduce the amount of code within your web pages. This will also cut down on the amount of web space and bandwidth used thus saving you money for hosting your site.

5. Easier to update and maintain web site

With no mistakes in your html code it is easier and faster to make changes to your web pages. For web site designers, this means you will save time and money when maintaining clients’ sites.

6. Browser compatibility

Validated code ensures your site is compatible with the current browsers and future browsers. You might say “well, it looks fine in Internet Explorer, so why bother with any other browsers?” Current browsers will continue to update their rules and future browsers will make sure they are html compliant.

7. Access more visitors

If you ensure your web pages appear correctly in all the major browsers you will be able to reach a larger audience which then increases the potential of your site to make more sales.