What if the website is good at first then it it changed later to a bad site? How do we know if it changed?If the blogs where you are linking the guest blog posting to are good quality blogs then that should help the SEO for your own blog perhaps.
You just want to make sure that you are not linking back to bad sites or that might hurt the SEO of your own blog.
so guest blogging on high authority websites increases authority? I though that the quality of your content does that.Guest Blogging is really a great way to increase traffic and gaining quality backlinks. You can do guest blogging on relevant high authority websites which will help you to increase your website traffic and also help you to build your authority online.
We should only do a little guest blogging so we don't get problems from the algorithms of search sites?Guest blogging if done in moderation can be good for SEO. Today as content has become even more important to and the search engine algorithms can recognise the good content. Thus guest blogging is good for SEO.
Why though? Maybe because of link building?Guest blogging is one of the best way of Off page SEO.