If you have another web browser installed, you can try to reproduce the problem in both. Failing this, you can describe your problem at Wikipedia:Village pump (technical) and ask other Wikipedians if they are having a similar problem. If no one else is, it's probably a problem with your particular browser setup.
Some, but not all, images don't show up. What's wrong?
Usually this is caused by ad-blocking software; uploaded files are distributed into random subdirectories, and 1/256th of all images on the server end up in http://upload.wikimedia.org/wikipedia/en/a/ad/, which trips off some advertisement-blocking proxies. Configure your proxy to allow this directory, and you should be fine.
I object to the very concept of Wikipedia. How can you expect me, or anyone, to take it seriously?
Not really. You need to be an administrator to delete pages. Any user can remove the text of a page, but another user usually restores the text from the history archive within a matter of minutes. If someone begins an extensive attack, they will be blocked from further editing by the admins. Moreover, there are periodic backups kept of the server itself. For more on this topic, see this discussion of "wiki wipeouts" at the original Wiki.
Is it possible for spammers to advertise on Wikipedia?
Unfortunately, spammers can and often do add spam to Wikipedia pages. Fortunately, anyone can quickly revert to a spam-free version of the page; it's so simple that most spam is eliminated within minutes. See Help:Reverting for what to do if you happen to be the first on the scene.
If you are looking to have your business mentioned favorably (or at all) in Wikipedia please read the Business FAQ.
If you see an article including inadequately attributed text or images – or, worse, copyright violations – please tell us about it in the "talk" page of that article. Then report it at Wikipedia:Copyright problems.
There's a dotted box around my newly added article, which is now a long line of words. What should I do?
Remove the space before the first word. When you need to indent a section of text you can use a colon (as has been done with this paragraph), but the first words of Wikipedia paragraphs are not indented. For more information on formatting, see the Manual of Style.