One of the great things about popular website platforms these days is the often bewildering number of modifications and add-ons that are available to customise your website from the basic out-of-the-box version. However, if you’re concerned about making sure that your web pages are correctly displayed and don’t break people’s browsers – and you should be, otherwise you may be driving away traffic! – it pays to be a little bit careful about which add-ons you choose.
Generally, the basic version of a website platform – like phpBB (the popular forum software) or WordPress (the software that powers this blog and countless others worldwide) – generates standards-compliant code (most commonly HTML or XHTML) if it’s not tampered with. Many of the plugins or mods that are written to accompany them are carefully tested to ensure that they work properly within the basic version and don’t mince up the page code. But, on the other hand, many of them aren’t. And even with the ones that are, it may be that your server software exposes a bug that the original script author’s test server didn’t.
So be sure to go back and revalidate your pages whenever you’ve installed a new plugin, to make sure that they still meet the standards. It’s worth revalidating from time to tame anyway, even if you haven’t added any new plugins – your hosting provider may have updated the server software.
The World Wide Web Consortium (W3C) have several tools to help you do this – the most useful is their Markup Validation Service, but they also have one for CSS stylesheets among others.