Have you ever noticed your text seem to jump when you have a blue link with a red hover? Here's a sample, Notice the pixel shift:
This text should highlight red when you hover over it
The fact is, it does move, it moves 1/3 of a pixel on a traditional monitor. Monitors are made of RGB blocks, when you turn one off and turn on another, it makes your text seem to jump over just a bit.
So when you're placing some links and it looks like they might be moving, try a color closer to your original link.