Using advertising on a website or blog has some things to think about. Here is a brief guideline on how and what to look while using the advertising.
This a matter of fact that bloggers and webmasters need to earn money through advertising and maybe a nice extra income can come out of it.
Legal issues with using advertising
When you are using advertising on your blog or website, it will be considered as a potential source of income (there are exceptions, we are talking about a person like me). So, you have to pay income tax. Nobody loves the income tax calculation things, but for legal purpose, you have to show the full documents as a proof of getting paid by advertising companies. Generally, there are some IT expert who does the things behalf of the first party for a small remuneration, at least this is widely used method in India.
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Not paying taxes for the money earned through advertising not only can place you behind the bars but also, the domain registration can be canceled.
Other than that, it is better to use a page named Advertising policy if you need it.

SEO issues with advertising
Advertising companies using Java scripts are better than a hard coded HTML code as Google crawler might escape through a textual link. On the other hand, Javascripts can be blocked at browser level but text advertising can not be blocked.
Some advertising companies opt in for opening the advertisement in a new window, there by the click is not counted as a visitor bounce. But some advertising companies (like Google Adsense) opt out this feature. Obviously, one click on the advertisement unit will show as a bounce.
We use Lake Quincy Media’s advertising, if any one click on a banner, that advertising unit will open in a new window, there by it will not be counted as a bounce.
Some CPM based advertising companies has the bad habit of putting some code in some advertisement, those will create a redirection automatically when the visitor wants to visit the page; for example; we used Dex Platform ago, they had this problem; when visitors clicked on our website link found in Google search, the page after loaded, it automatically redirected to a third party’s page.
Also check the advertising company’s profile by searching in Google with the domain name. If the first link is not of that domain, its blacklisted by Google, avoid it. Read the reviews of the advertising company in various blogs too.
Malware issues with advertising
Unknown, little known or badly known advertising companies can push malwares through advertising units.
Payment problems with the advertising companies
Search different blogs (or ask directly) whether the advertising company pays rightly. You can always file a criminal case against the advertising company for non payment issues, if you are not guilty.
Also use Newspapers and other media to alert people about that advertising company.

Quite good topic.
Thanks :)