What are header tags? They are simply paragraph headings and they are very important to SEO, as search engine spiders check them to help decide which keyterms the page is relevant for. H1, H2, H3, H4, H5 and H6 header tags also make things easier for the reader to quickly find the information that they …
Modify HTTP Headers (Examples) Many examples that show how to use the header() function of PHP
Controlling how web pages are cached is basically done using 2 kind of headers: Expires and Cache-Control
If you want to check your headers, you can use web based tools like: web-sniffer.net, web-browser extensions (e.g. LiveHTTPHeaders, ieHTTPHeaders) or another third-party software tool.