{"rowid": 330, "title": "An Explanation of Ems", "contents": "Ems are so-called because they are thought to approximate the size of an uppercase letter M (and so are pronounced emm), although 1em is actually significantly larger than this. The typographer Robert Bringhurst describes the em thus:\n\n\n\tThe em is a sliding measure. One em is a distance equal to the type size. In 6 point type, an em is 6 points; in 12 point type an em is 12 points and in 60 point type an em is 60 points. Thus a one em space is proportionately the same in any size.\n\n\nTo illustrate this principle in terms of CSS, consider these styles:\n\n#box1 {\n font-size: 12px;\n width: 1em;\n height: 1em;\n border:1px solid black;\n}\n\n#box2 {\n font-size: 60px;\n width: 1em;\n height: 1em;\n border: 1px solid black;\n}\n\nThese styles will render like:\n\n M\n\nand\n\n M\n\nNote that both boxes have a height and width of 1em but because they have different font sizes, one box is bigger than the other. Box 1 has a font-size of 12px so its width and height is also 12px; similarly the text of box 2 is set to 60px and so its width and height are also 60px.", "year": "2005", "author": "Richard Rutter", "author_slug": "richardrutter", "published": "2005-12-02T00:00:00+00:00", "url": "https://24ways.org/2005/an-explanation-of-ems/", "topic": "design"} {"rowid": 318, "title": "Auto-Selecting Navigation", "contents": "In the article Centered Tabs with CSS Ethan laid out a tabbed navigation system which can be centred on the page. A frequent requirement for any tab-based navigation is to be able to visually represent the currently selected tab in some way.\n\nIf you\u2019re using a server-side language such as PHP, it\u2019s quite easy to write something like class=\"selected\" into your markup, but it can be even simpler than that.\n\nLet\u2019s take the navigation div from Ethan\u2019s article as an example.\n\n
\n\nAs you can see we have a standard unordered list which is then styled with CSS to look like tabs. By giving each tab a class which describes it\u2019s logical section of the site, if we were to then apply a class to the body tag of each page showing the same, we could write a clever CSS selector to highlight the correct tab on any given page. \n\nSound complicated? Well, it\u2019s not a trivial concept, but actually applying it is dead simple.\n\nModifying the markup\n\nFirst thing is to place a class name on each li in the list:\n\n \n\nThen, on each page of your site, apply the a matching class to the body tag to indicate which section of the site that page is in. For example, on your About page:\n\n...\n\nWriting the CSS selector\n\nYou can now write a single CSS rule to match the selected tab on any given page. The logic is that you want to match the \u2018about\u2019 tab on the \u2018about\u2019 page and the \u2018products\u2019 tab on the \u2018products\u2019 page, so the selector looks like this:\n\nbody.home #navigation li.home,\n body.about #navigation li.about,\n body.work #navigation li.work,\n body.products #navigation li.products,\n body.contact #navigation li.contact{\n ... whatever styles you need to show the tab selected ...\n } \n\nSo all you need to do when you create a new page in your site is to apply a class to the body tag to say which section it\u2019s in. The CSS will do the rest for you \u2013 without any server-side help.", "year": "2005", "author": "Drew McLellan", "author_slug": "drewmclellan", "published": "2005-12-10T00:00:00+00:00", "url": "https://24ways.org/2005/auto-selecting-navigation/", "topic": "code"} {"rowid": 319, "title": "Avoiding CSS Hacks for Internet Explorer", "contents": "Back in October, IEBlog issued a call to action, asking developers to clean up their CSS hacks for IE7 testing. Needless to say, a lot of hubbub ensued\u2026 both on IEBlog and elsewhere. My contribution to all of the noise was to suggest that developers review their code and use good CSS hacks. But what makes a good hack?\n\nTantek \u00c7elik, the Godfather of CSS hacks, gave us the answer by explaining how CSS hacks should be designed. In short, they should (1) be valid, (2) target only old/frozen/abandoned user-agents/browsers, and (3) be ugly. Tantek also went on to explain that using a feature of CSS is not a hack.\n\nNow, I\u2019m not a frequent user of CSS hacks, but Tantek\u2019s post made sense to me. In particular, I felt it gave developers direction on how we should be coding to accommodate that sometimes troublesome browser, Internet Explorer. But what I\u2019ve found, through my work with other developers, is that there is still much confusion over the use of CSS hacks and IE. Using examples from the code I\u2019ve seen recently, allow me to demonstrate how to clean up some IE-specific CSS hacks.\n\nThe two hacks that I\u2019ve found most often in the code I\u2019ve seen and worked with are the star html bug and the underscore hack. We know these are both IE-specific by checking Kevin Smith\u2019s CSS Filters chart. Let\u2019s look at each of these hacks and see how we can replace them with the same CSS feature-based solution.\n\nThe star html bug\n\nThis hack violates Tantek\u2019s second rule as it targets current (and future) UAs. I\u2019ve seen this both as a stand alone rule, as well as an override to some other rule in a style sheet. Here are some code samples:\n\n* html div#header {margin-top:-3px;}\n.promo h3 {min-height:21px;}\n* html .promo h3 {height:21px;}\n\nThe underscore hack\n\nThis hack violates Tantek\u2019s first two rules: it\u2019s invalid (according to the W3C CSS Validator) and it targets current UAs. Here\u2019s an example:\n\nol {padding:0; _padding-left:5px;}\n\nUsing child selectors\n\nWe can use the child selector to replace both the star html bug and underscore hack. Here\u2019s how:\n\n Write rules with selectors that would be successfully applied to all browsers. This may mean starting with no declarations in your rule!\n\ndiv#header {}\n.promo h3 {}\nol {padding:0;}\n\n \nTo these rules, add the IE-specific declarations.\n\ndiv#header {margin-top:-3px;}\n.promo h3 {height:21px;}\nol {padding:0 0 0 5px;}\n\n \nAfter each rule, add a second rule. The selector of the second rule must use a child selector. In this new rule, correct any IE-specific declarations previously made.\n\ndiv#header {margin-top:-3px;}\nbody > div#header {margin-top:0;}\n\n.promo h3 {height:21px;}\n.promo > h3 {height:auto; min-height:21px;}\n\nol {padding:0 0 0 5px;}\nhtml > body ol {padding:0;}\n\n \n\nVoil\u00e0 \u2013 no more hacks! There are a few caveats to this that I won\u2019t go into\u2026 but assuming you\u2019re operating in strict mode and barring any really complicated stuff you\u2019re doing in your code, your CSS will still render perfectly across browsers. And while this may make your CSS slightly heftier in size, it should future-proof it for IE7 (or so I hope). Happy holidays!", "year": "2005", "author": "Kimberly Blessing", "author_slug": "kimberlyblessing", "published": "2005-12-17T00:00:00+00:00", "url": "https://24ways.org/2005/avoiding-css-hacks-for-internet-explorer/", "topic": "code"} {"rowid": 329, "title": "Broader Border Corners", "contents": "A note from the editors: Since this article was written the CSS border-radius property has become widely supported in browsers. It should be preferred to this image technique.\n \n \n \n A quick and easy recipe for turning those single-pixel borders that the kids love so much into into something a little less right-angled.\n\nHere\u2019s the principle: We have a box with a one-pixel wide border around it. Inside that box is another box that has a little rounded-corner background image sitting snugly in one of its corners. The inner-box is then nudged out a bit so that it\u2019s actually sitting on top of the outer box. If it\u2019s all done properly, that little background image can mask the hard right angle of the default border of the outer-box, giving the impression that it actually has a rounded corner.\n\nTake An Image, Finely Chopped\n\n\n\nAdd A Sprinkle of Markup\n\nLorem ipsum etc. etc. etc.
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