The price of a Kindle might dive in these next few days. Heck, for all you know, Torrentleech might open subscriptions again. There's a lot of stuff that you should keep an eye on. It certainly pays off.

Weeks, or even months later, you stumble about that same page again. The old Kindle is no longer available, and subscriptions have closed again. Oh, right. You forgot. Whether your habit of procrastinating, bad memory, or family-man attitude is to blame, the results are the same. The window of opportunity has closed.

There's no reason to rely solely on your own time and memory. Technology gives you the means to tame this online flux. You used to need a scripted macro for stuff like this. Right now, keeping track of website changes is as simple as a Google Chrome extension. Remember, "luck is what happens when preparation meets opportunity".

Page Monitor

Page Monitor is the Chrome equivalent of Firefox's Update Scanner Add-On. You can use it to track website changes. The learning curve for setting up a standard monitor is next to nothing, but the opportunities are endless.

You can use it to keep track of prices on Amazon or eBay, monitor Wikipedia page contributions, or watch private torrent trackers and Beta programs for that fleeting door of opportunity. If you're up to the advanced tweaking, you can even track certain elements within a page, like the first result in a Bing or Google search.

Configuring The Page Monitor Watchdog

Navigate to the page you're interested in and hit the top-right icon, next to your address bar. Start tracking website for changes with Monitor This Page. You can disable these monitored pages in the Options, or when a notification pops up, as well as specify the refresh timeframe.

Once something changes on the webpage, the icon will light up green. Page Monitor tries to ignore some ever-changing and superfluous page elements, like advertisements.

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The previously empty menu will now show a list of websites that require your attention - visit, mark as read, or call up a detailed overview of the changes.

Advanced Monitoring Options

At the bottom of the page, you can specify how long goes between every check-ups. By default, it's set to 180 minutes, or 3 hours. There's no real need to change this. Remember that more refreshes will require a bigger part of your computer memory. Checking for updates every minute can be tempting, but will noticeably impact your browsing. By expanding the advanced options, you can override the timeframe for each individual entry.

The other advanced monitoring options are a bit more complicated, and not all of them accessible for your average internet user, even with an explanation.

You can choose to monitor only a specific part of the page by using Regex (Regular Expressions) and Selector expressions. Both allow you to script certain elements to Page Monitor's attention.

Regex allow you to pick out different elements and words, depending on the context. For example, you can look for a price that's preceded by a specific set of words, or when it ends a sentence. Suffice it to say that Regex, although not ridiculously complicated, can not be taught in a single paragraph. If you want to take a closer look, you can read up via Wikipedia, where there's a concise introduction and guide to Regex. In the screenshot above, <b class="priceLarge">(.*?)<.b> has isolated the 'price' expression on Amazon and will track every future change.

One can also use the Regex input to search for a simple string of text and/or numbers. For example, in the screenshot above, I'm subsequently tracking two Amazon objects by respectively a 'real' Regex expression, and the absolute price. The latter, although easy to use, is limited by the two bolean values: true or false. It can only track the transition from presence to absence, and reversed. In the above example, it will note the price change from 55.49 to 50.49 (true to false) and back to 55.49 (false to true), but not from 50.49 to 60.49 (false to false), and any other creative transitions that don't feature the original Regex value. As such, you'll constantly need to revise said value. In other situations, e.g. the Torrent Tracker, using improvised Regex is a lot simpler. You'll only ever need to keep track of one sentence: Signups are closed.

Know any tips or alternatives to track website changes? Let us know your thoughts on Page Monitor in the comments section below!