I've seen in some websites such as http://twomovies.name/watch_movie/Shutter_Island that visited links are striked.
Is this good practice?
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Striking through signifies a revision or marking something as invalid. The established practice for visited link is a change in color, usually a less colorful or less saturated color from the original unvisited link's color.
Using striked through text is a poor choice, as it is ambigious: Is a striked link no longer valid? Is a striked link not recommended? Furthermore, it impacts readability, as it can be hard to figure out the original text once it is striked through.
I understand the need to visually stand out, but striked-through text breaks established patterns and therefore I would personally avoid using this method.
An less severe alternative I have seen is using different types of underlining for links -- i.e. unvisited links are underlined with a solid line, visited links underlined with a dotted or dashed line. While the negative or ambiguous impact is less, dotted underlined words are commonly used for acronyms or other text that shows a tooltip on hover.
I can see it being useful if you want to the user to get the message "you have been here, and never need to go back"... otherwise, color change is a better, more universal option.
I always find it weird to click on links that are strikethrough, especially if the rollover adds an underline... With two extra horizontal lines, it's a bad case of 1+1=3 and you can hardly read the text underneath.
Even though a visited link changes in appearance, it generally continues to be a valid link that can be clicked exactly as before to access the url linked to. This is the established convention.
In a slightly different scenario, consider a link that may be valid only once — after which the user cannot or will not click on it ever again. In such a paradigm, it does make sense to show the link in