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Configuring and Administering Your Server >>
DNS
"For people who make websites" - A List Apart Magazine explores the design, development, and meaning of web content, with a special focus on web standards and best practices.
HTML Validator is a Mozilla extension that adds HTML validation inside Firefox and Mozilla. The number of errors of a HTML page is seen in the form of an icon in the status bar when browsing. The details of the errors are seen when looking the HTML source of the page.
The extension is based on Tidy and OpenSP. Both algorithms were originally developed by the Web Consortium W3C. Both algorithms are embedded inside Mozilla/Firefox and makes the validation locally on your machine, without sending HTML to a third party server.
The extension is based on Tidy and OpenSP. Both algorithms were originally developed by the Web Consortium W3C. Both algorithms are embedded inside Mozilla/Firefox and makes the validation locally on your machine, without sending HTML to a third party server.
This project aims to create an archive of user contributed clip art that can be freely used.
Starting at the beginning, this reference explains everything you need to know about using core JavaScript. It assumes you have the following basic background: a general understanding of the Internet and the World Wide Web and a good working knowledge of HTML. An excellent resource.
Edit your images on the fly online with Splashup, a web-based image editor that integrates with Flickr, Facebook, and Picasa. Splashup offers up a surprising array of image editing tools, far beyond the usual crop of resize and contrast-- you can also edit multiple images, play with filters and layers, use a variety of brushes, and more. Splashup is one of the best image editors in a long line of image editors; i.e., Picnik, Pixoh, and Resizr, to name just a few.[Lifehacker Annotation]
This website will let you:
- Create an XML sitemap format that can be submitted to Google to help them crawl your website better.
- Create a Text sitemap to submit to Yahoo.
- Create a ROR sitemap, which is an independant XML format for any search engine.
- Generate an HTML site map to allow human visitors to easily navigate on your site.
Clearspring's free Launchpad widget builder lets you easily turn your website's content into a widget which site visitors can use to place your content on all the major social media sites (MySpace, FaceBook, Google, hi5, Live, Yahoo, Wordpress, Blogger, etc.). The service also provides tracking and analysis.
This site features online text and html changing, modifying, converting tools designed to save you time making web pages or preparing text for web publication. If you've ever needed to capitalize sentences or convert line breaks to <p> or <br /> then this site can save you needless manual labor. There are other useful tools as well, like the one to uncompress html to make it readable and the ones to uppercase or lowercase text. Basically, the most common tasks that someone who works in an office or does freelance web development might encounter. Most of the tools have been created using javascript so you should be able to change large amounts of text as the processing is done on your computer instead of being limited by a server script.
You've downloaded and configured your Apache server and are ready to move on to the next project. Can it really be left to fend for itself in a darkened room?
Yes. To some degree, anyway. On the other hand, completely ignoring your Apache installation would be foolhardy.
Yes. To some degree, anyway. On the other hand, completely ignoring your Apache installation would be foolhardy.
The Wikipedia entry for Sender Policy Framework (SPF).
The Wikipedia entry for DomainKeys.
Useful Resources
View all resources
Editor Favorites
- A List Apart
- HTML Validator Firefox Plugin
- Open Clip Art Library
- Core JavaScript Guide: Version 1.5
- Splashup
- XML Sitemaps Generator
- Clearspring Launchpad
- Text Fixer
Other Resources
Links to Consider
The DNS system is, in fact, its own network. If one DNS server doesn't know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.
Generally speaking, your webhost will probably take care of any relevant DNS related issues. Typically, all you have to do is specify the DNS servers (typically two) with your domain name registrar and then never worry about it again. For those with virtual or dedicated servers, more control over DNS functionality may be possible.
While proper DNS configuration is a must for your site to be accessible to the world, you may or may not be aware that it is also a crucial piece of the email puzzle. That's because servers can use DNS to validate that the sending IP of received email matches the domain name being represented as the source for that email. Below are typical tests used to validate email.
DNS Authentication Tests Run by Email Servers:
Validating the IP address of the SMTP client:
- Do a reverse lookup (query DNS for the pointer (PTR) record of the sender's IP address)
- If no reverse lookup for the IP succeeds, then reject the mail.
- Check if the returned PTR record refers to the HELO/EHLO hostname. If not, reject the mail.
- Does the returned hostname have an address (A) record? If not, reject the mail.
- Does the PTR hostname have a Mail Exchange (MX) record? If not, reject the mail.
Validating the HELO/EHLO hostname information:
- Does the hostname resolve to a DNS A or MX record? If not, reject the mail.
- Is the hostname a FQHN: Fully Qualified Host Name? If not, reject the mail.
Validating the MAIL FROM: @sender.domain information:
- Does sender.domain resolve to a DNS A or MX record? If not, reject the mail.
- Is sender.domain a FQHN: Fully Qualified Host Name? If not, reject the mail.
Notes:
- Some servers don't return MX records as a policy (for various reasons).
- In addition to DNS validation, many servers query one of the MAPS databases for black-holes, open-relays, or dial-ups. If it finds the IP address listed the mail will be rejected.
- Alternative methods for email verification have been developed and are becoming increasingly important. Specifically, refer to the entry for SPF, SenderID and DomainKeys.
Things to Do:
- Make sure your DNS has been delegated with reverse authority. There are many resources out there, but you can visit AOL's Reverse DNS Check to verify your server is setup properly.
- Perform more complete DNS tests at the DNS Report site and/or CheckDNS.net. You will learn a lot by reading explanations of all the tests performed. Pay attention especially to the failures and warnings (they're not all dire, but definitely make sure that you don't fail the open relay test).
- Make sure your server has an SPF record.
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