My blog

I make changes to this web site frequently but because they are buried somewhere on one of the pages they are not very noticeable, so I have decided to create this blog to highlight significant new material. In the pages below you will find part of one of the pages that I have either changed or added to significantly.

The Customer's Watches page that used to be here can now be found under the Designs and Ordering menu item.

A page about Simple Harmonic Motion and how it enables watches to keep accurate time can be found at Simple Harmonic Motion.

A page about Moments of Inertia, and why they depend on the square of distance from the centre of rotation, can be found at Moment of Inertia.

A page about Centripetal Force can be found at Centripetal Force.

A page testing web fonts can be found at typography.

A page testing the appearance of equations can be found at Equations.

Force browser to reload modified CSS file

Browsers cache files so that they don't have to be loaded every time a web page is viewed. This can be problematic with css and image files, where the browser stubbornly refuses to load a later version of a file with the same name. A browser can be forced to reload a modified CSS, or a modified image file, using versioning.

This can be done manually by adding a query string parameter to the URL of the file, e.g. a question mark (?) followed by a version number. Changing the version number will force the browser to reload the file.

	
		<link rel="stylesheet" href="style.css?v=1.0" >

Manual versioning is tedious, because it requires the version number to be changed on each page the file is referenced every time the file is updated. The php function filemtime() can be used to automatically change the version number when the file is updated.

	
		<link rel="stylesheet" href="<?php echo 'style.css' . '?v=' . filemtime('style.css'); ?>" >

Note that the filemtime() only changes when the file is actually modified, so this does not interfere with normal browser caching. The same method works for image files.

If you have any comments or questions, please don't hesitate to get in touch via my Contact Me page.