What can I do to boost Internet Explorer 8 VML rendering speed?

Rendering VML in standards mode in IE8 is about 10 times slower compared to IE8 quirks/compatibility mode or previous IE versions! You can force the page to always use compatibility mode in IE8 by adding the following to the head section (before any other tags):
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
This tag, when seen by IE8 will render the page in IE7 compatibility mode regardless of whether or not you’ve set IE to run in IE8 Standards mode or not.

With Internet Explorer nothing happens by using img onload event?

Internet Explorer behaves strange on using the <img onload="cvi_glossy.add(this)" ... /> event! You can force the page to execute the cvi_glossy.add() function by using the window.onload event. Do the following: Instead of using...
<img onload="cvi_glossy.add(this)" src="image.jpg" alt="" />
...add an ID and remove the event...
<img id="my_img" src="image.jpg" alt="" />
..then create this section...
<head>
...
<script type="text/javascript">
<!--
window.onload = function () {
    cvi_glossy.add(document.getElementById("my_img"));
};
-->
</script>
</head>
Another solution is to execute the following before any other code:
<head>
...
<script type="text/javascript">
<!--
if(document.all&&document.namespaces&&!window.opera) {
    if(document.namespaces['v']==null) {
        var e=["shape","shapetype","group","background","path","formulas","handles",
        "fill","stroke","shadow","textbox","textpath","imagedata","line","polyline",
        "curve","roundrect","oval","rect","arc","image"];
        var s=document.createStyleSheet();
        for(var i=0; i<e.length; i++) {
            s.addRule("v\\:"+e[i],"behavior: url(#default#VML);");
        }
        document.namespaces.add("v","urn:schemas-microsoft-com:vml");
    }
}
-->
</script>
</head>
[NOTE: Exchange glossy with the script name you want to use]
...and you're good.

What's that? "Internet explorer cannot open the internet site... operation aborted"

Internet Explorer doesn't like the open <base> tag. Do the following: Exchange...
<base href="http://www.yourdomain.com/">
...or...
<base href="http://www.yourdomain.com/" />
...with...
<base href="http://www.yourdomain.com/"><!--[if IE]></base><![endif]-->
...and you're good.

Your script kills the wrapping behavior implemented by style declaration (e.g. float)!

No and yes! Yes, if you set a class/id/behavior to work only on <img> tags. For example:
img.floatleft {margin: 5px; float: left; }
This is because the scripts exchange image elements with canvas or vml elements! To solve the problem you can add...
img.floatleft, canvas.floatleft, var.floatleft {margin: 5px; float: left; }
...or simply remove the tag restriction...
.floatleft {margin: 5px; float: left; }
...and you're good.

Your script kills the alignment behavior implemented by align="right"!

No and yes! Yes, if you set the alignment through html attribute align. For example:
<img src="..." align="left" hspace="2" border="0">
This is because the scripts exchange image elements with canvas or vml elements and canvas do not support align (The attributes [align|hspace|vspace|border] are deprecated if used in <img>)! To solve the problem you can add the style attribute...
<img src="..." style="float: left; margin-right: 4px;">
...or add the class attribute like...
.floatleft {margin-right: 4px; float: left; }
<img src="..." class="floatleft">
...and you're good.
If you need other alignments like [top|middle|bottom], or you don't want to use style sheets, solve it by embedding the image in a div...
<div align="middle"><img src="..."></div>
...and you're good.

It seems that your script is not compatible with jQuery?

There is no jQuery incompatibility in conjunction with cvi scripts/libs known! But jQuery's selector function behaves different than e.g. Prototype's.
jQuery searches through the DOM for the element that match the provided selector and creates a new jQuery object that references these element!
Prototype and the JS function getElementById searches through the DOM for the element that match the provided selector and returns that element!
To solve the problem you need to modify your code like this...
<script type="text/javascript">
<!--
window.onload=function() {
    //The code below won't work
    //transm.add($("wrapper"),options);
    //The code below will work very well
    transm.add(document.getElementById("wrapper"),options);
};
-->
</script>
[NOTE: Exchange transm with the script name you want to use]
...and you're good.

Your script do not work with other existing <body onload> scripts?

To use the body onload event is an outdated programming technique. The body onload event get in conflict with the window.onload event. To solve the problem you need to modify the page like this...
<body onload="your_function();"> ...to... <body>
..then create this section...
<head>
...
<script type="text/javascript">
<!--
window.onload = function () {
    your_function();
};
-->
</script>
</head>
[NOTE: Exchange your_function with the function name you are using]
...and you're good.

Is it possible to hide images, so the transition can not be seen?

To solve the problem you can add the following lines to the <head> section of your page...
<script type="text/javascript">
<!--
var canvascheck = document.createElement('canvas');
if(canvascheck.getContext || (document.all && document.namespaces && !window.opera)){
    document.writeln('<style type="text/css">');
    document.writeln('img.glossy { visibility: hidden; }');
    document.writeln('<\/style>');
}
-->
</script>
<script type="text/javascript" src="glossy.js"></script>
[NOTE: Exchange glossy with the script name you want to use]
...and you're good.

Is it possible to use «onmouseover», «onmouseout» functions in your scripts?

To solve the problem you need to use the cvi_*_lib.js version of the script. Add a surrounding div to the <img> like this...
<div
onmouseover="cvi_strip.modify(this.firstChild,{strip:100});"
onmouseout="cvi_strip.modify(this.firstChild,{strip:80});">
<img onload="cvi_strip.add(this,{strip:80});" src="image.jpg" border="0" alt="">
</div>
[NOTE: No spaces and no return between the div and the image e.g. <div><img></div>]
[NOTE: Exchange strip with the script/lib name you want to use]
...and you're good.

With instant.js, the image proportions seems to be compressed/stretched.

Yes. This is because of the border width, which is the same for height and width. Therefor the aspect ratio of the image will be compressed/stretched a little bit. This effect grows it the ratio of width and height differs from the aspect 1/1 and starts to be noticeable at an aspect of 3/2. Since version 1.5 you can use the class "preserve" to preserve the aspect ratio.

My anti-virus program raised a warning saying that the script includes an exploit.

Under certain circumstances with a heuristic search the exploit "EXP/HTML.VML.Gen" will falsely be discovered in "Corner.js" only. I would fix it if the circumstances would be known, but even the virus-checker manufacturer couldn't tell me why!
The initialization of the VML support ...
document.namespaces.add("v", "urn:schemas-microsoft-com:vml");
... seems to release the virus warning!

I've tried the scripts in IE8 beta and it doesn't seem to be working?

Internet Explorer 8 beta releases are partially in worse shape. They don't support VML in strict mode even if you're running in IE7 mode. Support for binary layout/rendering behaviors, of which VML is an example, is implemented in IE8 since the final release - which works perfectly.

None of the scripts are working anymore in Firefox 2.0.0.10!

"error: uncaught exception: [Exception... "Component returned failure code: 0x80040111 (NS_ERROR_NOT_AVAILABLE) [nsIDOMCanvasRenderingContext2D.drawImage]" nsresult: "0x80040111 (NS_ERROR_NOT_AVAILABLE)"

 Firefox 2.0.0.10 has several new bugs.
One of them is canvas.drawImage is not working in this version. The bug has already been fixed and the new version 2.0.0.11 is now available. You can also degrade to an older version e.g. 2.0.0.9.