Try not to make links a major part of your answers, then you have nothing to worry about!
For example, if you want to link to Terry Tao's blog, then link too it and include a nice quote from it or a brief summary which gets your point across. For example, do this rather than this.
I think wikipedia links, and indeed internet links in general, should be only used for one of the following*.
"For more information" links. That is, you explain something and then you say "for more information, see here".
Defining something they they really should know using a link. The reader could look up "normal subgroup" in a book, you are just being helpful and saving them time. Plus, they really shouldn't need to look it up.
A link to a, for example, quotation you are using (as with the Terry Tao blog example, above).
This is for two reasons.
- If an answer is heavily reliant on links then it is susceptible to "link rot", where the website linked to stops functioning and so the answer is invalidated. (Note the use of the "for more information" link!) EDIT: A genuine example of industrial-scale link rot can be found here, when Springer encyclopedia of mathematics changed its website.
- It means that your answer is self-contained, which is pleasing. Moreover, I don't want to have to click on a link to work out what on earth you are going on about!
*These are the only reasons I could think of at the time of writing. I am sure there are more, so feel free to suggest them. Nor do I believe that there are no exceptions.