Highlighting text selects the whole page?

[hitmann]

Sometimes when I highlight part of a text in some webpage, it highlights the remaining of the page from where I started to highlight. What is causing this? How to prevent it when I'm creating a website?

 

[Berserker]

Depends entirely on the browser, the page layout, and where you select to. I've seen cases where layout using tables does this (if you select below a cell it selects all the cells to the right), and I think CSS column layouts can do the same as well.