What is the meaning of the meta tag "EXPIRES"
The expires meta tag tells search engines when the content on your website will expire. The expires meta tag defines the expiration date and time of the document being indexed. If your website is running a limited time event or there is a preset date when your document will no longer be valid, you should include the expires tag to indicate to search engines when to delete your web-page from their database.
The expires tag is commonly used in conjunction with the Revisit Tag as a means to get search engines to re-visit a website every few days. This is commonly used by websites who update their content frequently and want search engines to have a fresh copy of their content.
If you replace or rename a web-page please use a 301 refer to point the seach engines in the right direction. Search engines will automatically replace the old page with the new page.
<meta name="expires" content="date">
Example how to use the meta tag expires
Add the following meta tag in the source of your web-page. The difference in spelling at the end of the tag is either you use " /> is for xml or "> is if you use html.
<meta name="expires" content="tue, 01 Jun 2010">
Make sure your date is in the RFC1123 format so a date as shown above: day, dd mm yyyy so the year in 4 digits.
Sometimes a specified time is used but this option is no longer supported by search engines.
<meta name="expires" content="tue, 01 Jun 2010 19:45:00 GMT">
Also you will see the value zero "0" to have the page deleted. A better way to do this is using the 301 refer in case of a new page or the 404 - not found.
<meta name="expires" content="0">
Where should you add this expires tag?
You may add this expires meta tag to all of your web-pages, so not only in the first index page. Make sure that on every page relevant meta tags are added. Add keywords and phrases that are relevant and correspond to the text and the language on that specific page. It might be a lot of work to add specific meta tags to each page but you will notice in time that it works!