SE visits go up and down, what's the problem?

About 3 months ago one of my sites lost half of it's daily visitors from google. That lasted for a month and a half and then it came back like nothing happened. Stayed that way for a while and then again half of visitors gone, for 10 days. Comes back again. Lasts for about 15 days and today it crashes again to half of it's usual daily visitors. Look at the graph, it's straight and then just falls and straight again.

Doesn't let me post an image. 1fyOFjM jpg on imgur

Wtf is happening? The site is quite old so it's not google dance. Must be some kind of link penalty?

what have you done in terms of link building in the last 3 months! may be it is just that your competition.

I haven't done anything really. I mean the site does have a lot of shitty links (not blog comments but lots of profile links, signatures, not too heavy on the anchor though) but I haven't done any real linking in 6 months maybe. What keeps the site so popular is that it's the best in the niche, it's videos, and people even google the brand name of the site quite a lot. I have been linking after the crash though. Got two sitewide links from PR2 domains but not with a direct keyword anchor. One was almost gibberish, the other was "something keyword something".

I have though been replacing broken videos before every crash but with the same videos. That should make the site better not worse. Could all the editing be causing the crashes?

What about niche. is this seasonal?

Nope. Not seasonal. The visits were very steady for years before this.

It might be, but why does it keep coming back? I'm sure that in 10-15 days the visits will return like they returned 2 times before this.

What are the rankings doing during these periods of lower activity?

It your server up to the job? If you are on shared hosting with WP and a large site with heavy traffic your hoster may be throttling you.

When you lose traffic is there a significant event in your niche that is distracting your audience?

I'm usually number one for my main keyword on a couple of versions of google (tld). When this happens I fall to 3 or 4, but it also seems that all the long tail visits are decreased too.

The server is fast, dedicated, could handle at least 40% more visits than this. There are no events, just some shittier sites than mine jump up in front of me.

Currently the PR of the one who's in front of me is "unranked" lol.

Then it seams like it is directly related to rankings slip.

This may mean that what once was a solid ranking is beginning to weaken.

Might be time to start some slow quality link building and content expansion.

I hate to be where you are, I almost never mess with a ranking page.