I've narrowed down my issue to a fairly simple case. This works (in Chrome, at least), displaying a "pop-up" which is mostly off-screen, with a slice of the right hand side on screen. When I hover over the visible part, the whole pop-up slides into view:
<!DOCTYPE html>
<html>
<head>
<title>Popout test</title>
<style>
#popout {
-webkit-transition: left 0.5s ease-in-out;
width: 200px;
height: 200px;
background-color: #cde;
border: 4px solid black;
padding: 4px;
left: -180px;
position: absolute;
top: 250px;
}
#popout:hover {
left: -4px;
}
</style>
</head>
<body>
<div id="popout">This is a test</div>
</body>
</html>
However, if I then move that exact CSS into an external stylesheet:
<!DOCTYPE html>
<html>
<head>
<title>Popout test</title>
<link rel="stylesheet" href="popout.css" />
</head>
<body>
<div id="popout">This is a test</div>
</body>
</html>
popout.css:
#popout {
-webkit-transition: left 0.5s ease-in-out;
width: 200px;
height: 200px;
background-color: #cde;
border: 4px solid black;
padding: 4px;
left: -180px;
position: absolute;
top: 250px;
}
#popout:hover {
left: -4px;
}
...the effect remains the same, but on page load the pop-up appears "popped out" and eases back off screen. With the style directly in a <style> in the html page, as in the first example, this doesn't happen; the pop-up starts "off screen", i.e. at left: -180px as I would expect.
I'm wondering if this is a "flash of unstyled content", with the added annoyance that because of the transition effect, it's actually a very obvious, slow effect?
Can anyone tell me for sure why this happens, and what's the least hacky way to avoid it?
Because of the way jsfiddle works, I can't reproduce the problem there, unfortunately.
