Basics
For controlling "cellpadding" in CSS, you can simply use padding on table cells. E.g. for 10px of "cellpadding":
td {
padding: 10px;
}
For "cellspacing", you can apply the border-spacing CSS property to your table. E.g. for 10px of "cellspacing":
table {
border-spacing: 10px;
border-collapse: separate;
}
This property will even allow separate horizontal and vertical spacing, something you couldn't do with old-school "cellspacing".
Issues in IE ≤ 7
This will work in almost all popular browsers except for Internet Explorer up through Internet Explorer 7, where you're almost out of luck. I say "almost" because these browsers still support the border-collapse property, which merges the borders of adjoining table cells. If you're trying to eliminate cellspacing (that is, cellspacing="0") then border-collapse:collapse should have the same effect: no space between table cells. This support is buggy, though, as it does not override an existing cellspacing HTML attribute on the table element.
In short: for non-Internet Explorer 5-7 browsers, border-spacing handles you. For Internet Explorer, if your situation is just right (you want 0 cellspacing and your table doesn't have it defined already), you can use border-collapse:collapse.
table {
border-spacing: 0;
border-collapse: collapse;
}
Note: For a great overview of CSS properties that one can apply to tables and for which browsers, see this fantastic Quirksmode page.
Either use a semi-transparent PNG or SVG image or use CSS:
background-color: rgba(255, 0, 0, 0.5);
Here's an article from css3.info, Opacity, RGBA and compromise (2007-06-03).
<p style="background-color: rgba(255, 0, 0, 0.5);">
<span>Hello, World!</span>
</p>
Best Solution
Rather than use some non-standard control, what you should be doing is using un-obtrusive javascript to do it after the fact. See http://code.google.com/p/jquery-checkbox/ for an example.
Using the standard ASP checkbox simplifies writing the code. You don't have to write your own user control, and all your existing code/pages don't have to be updated.
More importantly, it is a standard HTML control that all browsers can recognize. It is accessible to all users, and work if they don't have javascript. For example, screen readers for the blind will be able to understand it as a checkbox control, and not just an image with a link.