Here is this wonderful option available to setup advance alerts.
To create new alerts or configure advanced alerting options, click Start > All Programs > SolarWinds Orion > Alerting, Reporting and Mapping > Advanced Alert Manager on your Orion server.
I believe this should help.
Hi! yes, i know how to setup advanced alerts, but my question was, how do i go about the setting up alerts for custom pollers.
First off, 'has changed' is VERY misleading - it is only used to determine if the LastBoot has changed. 
There isn't (AFAIK) any way to determine if something has changed, which IMO is a pretty big gap in the product.
On the other hand, you are going about it the right way (picking out the PollerName like that).
 (CustomPollerStatus.RawStatus = CustomPollerStatus.RawStatus and ((select count(*) from AlertValueChanges where TableName = 'Nodes' and FieldName = 'LastBoot') > 0) and (NodeID in (select NodeID from AlertValueChanges where TableName = 'Nodes' and FieldName = 'LastBoot' and (DateDiff(s, Changed, getdate()) < (60 * 1.2)))) /* Do not remove this comment HAS1101CHANGEDTBL|FLDNodes|LastBootHAS1101CHANGED */)
Here is a possible way to do it.
In the Advanced Alert manager,Select a "New" option to create a one fresh.
In the "Trigger Condition" tab ,there is one drop-down option for the field "Type of Property to Monitor" named "Custom SQL Alert".Once this drop-down option is selected then you get another field added which says "Setup your Trigger Query"wherein you could select the option "Node".
Then below you get a page to key in the sql query.Now here is something which you need to find out to get this Query right.
So when you create a custom poller,a table will also be created in the database.So i would suggest you to look into the database to find out which table is having this particular information.Once you pick the table and so a step ahead to find out which field is the one which is collecting CSSs errors.This will get you job half done.
Considering the example mentioned in your initial thread,"For example, I've got OID 188.8.131.52.184.108.40.206.9.1.6 which polls for CSSs errors in node details page. This poller is named "CSSs" . I need an alert in Advanced Alerts that would notify me when this CSS value has changed.".Here is a possible query logic you could apply.
Say your CSSs errors is collecting a fixed value as "4352".So your query could be something like
select CSSs_errors from CSS_table where CSSs_errors<>'4352'
This query logic will satisfy your needs.
However in the same pop-up window there is one another tab named "Trigger Actions" which needs to be taken care so that you get an email or any kind of alert.I believe you must be able to handle this from here on.
Please let us know the results.