The target sentence can be put in this way "昨天我看到了你的网页，但是现在我又看不到。”
As the usage of “不看到” is not often to see, I assume you might mean to ask about the difference between "看不到“ and ”没看到“. Although they both can mean the same thing, there is slight difference between them.
- 看不到 means ＂I could not/ cannot see it" . (it is beyond my ability to see it)
- 没看到 means "I could/did not see it" (it is within my ability to see it, but other reasons on my side causing me fail to see it).
The difference can even be applied in other similar phrases,
such as "我听不到你说的，因为这里太吵了。”
As rare as the usage of “不看到”, you can still find it in sentences like this:
今晚不看到流星，我就不睡觉。（ If I cannot see the shooting star tonight, I will not go to bed.)
It is actually more of a sentence structure of " 不+verb..., subject+就不+ verb“