Do you have a lot of tabs open in chrome? If so, you are using a lot of memory, which each tab uses.
You can bookmark the site's, but this was always a problem for me on firefox and chrome.
The frequently used sites are stored as tab in the chrome extension "TooManyTabs for Chrome".
This extension allows to manage the tabs in different categories. Select the Icon and you can switch through the Categories. The yellow title bars on the right side are the saved tabs and the widows on the left are the open ones, which can be closed and moved to the category.
When you are in a tab a right click to get the context menu, allows you to send the tab to a category of